U.S. patent application number 11/372573 was filed with the patent office on 2007-04-12 for dynamic control of dilution ventilation in one-pass, critical environments.
Invention is credited to Eric M. Desrochers, Gordon P. Sharp.
Application Number | 20070082601 11/372573 |
Document ID | / |
Family ID | 36992261 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070082601 |
Kind Code |
A1 |
Desrochers; Eric M. ; et
al. |
April 12, 2007 |
Dynamic control of dilution ventilation in one-pass, critical
environments
Abstract
A dilution ventilation control system for use in a one-pass,
critical environments comprising: one or more one-pass, critical
environments comprising, a variable source of supply airflow
volume, an exhaust for completely exhausting the airflow volume
supply from the critical environment and from a building comprising
the critical environment through one or more exhaust ducts; and at
least one an airflow control device provided in one or more of the
ducts to vary the exhaust airflow volume from the critical
environment; a facility monitoring system comprising at least one
air contaminant sensor for sensing at least one air contaminant of
the critical environment; a signal processing controller that
generates one or more airflow command signals based at least in
part on at least one sensed air contaminant; and a critical
environment airflow controller that uses the airflow command signal
to at least partially control the critical environment's supply and
exhaust airflow volumes.
Inventors: |
Desrochers; Eric M.;
(Millis, MA) ; Sharp; Gordon P.; (Newton,
MA) |
Correspondence
Address: |
Mirick, O'Connell, DeMallie & Lougee, LLP
100 Front Street
Worcester
MA
01608
US
|
Family ID: |
36992261 |
Appl. No.: |
11/372573 |
Filed: |
March 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60660245 |
Mar 10, 2005 |
|
|
|
Current U.S.
Class: |
454/256 ;
454/239 |
Current CPC
Class: |
F24F 2110/70 20180101;
F24F 2110/50 20180101; G01N 1/2273 20130101; Y02B 30/70 20130101;
G01N 33/0063 20130101; F24F 3/0442 20130101; F24F 3/044 20130101;
F24F 2110/66 20180101; F24F 2110/10 20180101; F24F 2110/20
20180101; F24F 11/30 20180101; G01N 1/26 20130101; F24F 11/0001
20130101 |
Class at
Publication: |
454/256 ;
454/239 |
International
Class: |
F24F 11/00 20060101
F24F011/00 |
Claims
1. A dilution ventilation control system for use in a one-pass,
critical environments comprising: one or more one-pass, critical
environments comprising, a variable source of supply airflow
volume, a means for completely exhausting said airflow volume
supply from said critical environment and from a building
comprising said critical environment through one or more exhaust
ducts; and at least one airflow control device provided in one or
more of said ducts to vary the exhaust airflow volume from said
critical environment; a facility monitoring system comprising at
least one air contaminant sensor for sensing at least one air
contaminant of said critical environment; a signal processing
controller that generates one or more airflow command signals based
at least in part on at least one sensed air contaminant; and a
critical environment airflow controller that uses said airflow
command signal to at least partially control said critical
environment's supply and exhaust airflow volumes.
2. The dilution ventilation control system of claim 1, further
comprising one or more carbon dioxide sensors and; wherein said
signal processing controller generates one or more of said airflow
command signals based in further part on a level of carbon dioxide
in said critical environment sensed by said carbon dioxide
sensor.
3. The dilution ventilation control system of claim 1 wherein at
least one of said air contaminant sensors comprises a TVOC
sensor.
4. The dilution ventilation control system of claim 3 wherein said
TVOC sensor comprises a photo-ionization detector TVOC sensor.
5. The dilution ventilation control system of claim 1 wherein said
airflow command signal varies a dilution ventilation portion of
said critical environment's supply and exhaust airflow volumes.
6. The dilution ventilation control system of claim 1 wherein said
airflow command signal varies an offset airflow of said critical
environment.
7. The dilution ventilation control system of claim 6 wherein an
occupancy sensor is used to detect a reduction in occupancy in said
critical environment and said signal processing controller at least
partially reduces said airflow command signal for a dilution
ventilation portion of said critical environment's supply or
exhaust air volumes in response to said reduction in occupancy.
8. The dilution ventilation control system of claim 1 wherein said
facility monitoring system comprises a multipoint air sampling
system that transports one or more air samples from a plurality of
locations comprising at least said critical environment to one or
more shared air contaminant sensors.
9. The dilution ventilation control system of claim 8 wherein said
multipoint air sampling system is a star configured multipoint air
sampling system.
10. The dilution ventilation control system of claim 8 wherein said
multipoint air sampling system is a networked air sampling
system.
11. The dilution ventilation control system of claim 8 wherein said
signal processing controller uses said at least one of said shared
air contaminant sensors to generate at least one virtual sensor
signal.
12. The dilution ventilation control system of claim 11 wherein at
least one of said virtual sensor signals is in communication with a
building control system.
13. The dilution ventilation control system of claim 12 wherein at
least one of said virtual sensor signals is in communication with
the building control system through a data communications
means.
14. The dilution ventilation control system of claim 8 wherein said
air samples from said plurality of location are sampled by of the
multipoint air sampling system in a sequence that is based on an
output signal of said signal processing controller.
15. The dilution ventilation control system of claim 14 wherein
said sampling sequence of said multipoint air sampling system is
based on an output signal of said signal processing controller that
indicates a rapid rise in an amplitude of an air contaminant above
a trigger level.
16. The dilution ventilation control system of claim 1, further
comprising a room switch located in said critical environment to at
least partially control said critical environment's supply and
exhaust airflow volumes.
17. The dilution ventilation control system of claim 16 wherein
said room switch comprises an emergency exhaust switch.
18. The dilution ventilation control system of claim 1, wherein
said facility monitoring system comprises at least two sensors for
monitoring and wherein said signal processing controller generates
said airflow command signal based at least in part on at least said
two sensors.
19. The dilution ventilation control system of claim 18 wherein at
least one of said sensors comprises an occupancy sensor.
20. The dilution ventilation control system of claim 1 wherein said
plurality of locations including at least said critical environment
includes at least one location that involves sampling air from an
air duct that provides airflow into or takes air out of one or more
critical environments.
21. The dilution ventilation control system of claim 1 wherein said
airflow command signal comprises a discontinuous airflow command
signal.
22. The dilution ventilation control system of claim 21 wherein
said discontinuous airflow command signal comprises a two state
signal.
23. The dilution ventilation control system of claim 21 wherein
said discontinuous airflow command signal comprises a three state
signal.
24. The dilution ventilation control system of claim 21 wherein
said discontinuous airflow command signal comprises a multiple
state signal.
25. The dilution ventilation control system of claim 1 wherein said
airflow command signal comprises a continuously variable command
signal.
26. The dilution ventilation control system of claim 1 wherein said
plurality of locations comprises at least one location wherein said
air samples are indicative of one or more outdoor air
conditions.
27. The dilution ventilation control system of claim 1 wherein said
signal processing controller is implemented by one or more
components of a critical environment airflow control system.
28. The dilution ventilation control system of claim 1 wherein said
signal processing controller is implemented by one or more
components of a building control system.
29. The dilution ventilation control system of claim 1 wherein said
critical environment airflow controller is implemented by one or
more components of a critical environment airflow control
system.
30. The dilution ventilation control system of claim 1 wherein said
critical environment airflow controller is implemented by one or
more components of a building control system.
31. The dilution ventilation control system of claim 1 wherein said
airflow command signal increases both of said supply and exhaust
air volumes when said airflow command signal commands a greater
airflow than any other airflow command signals controlling said
supply and exhaust air volumes.
32. The dilution ventilation control system of claim 1 wherein said
signal processing controller generates an airflow command signal to
increase at least one of said supply and exhaust air volumes when
at least one air contaminant exceeds a threshold level or
approximately matches a signal pattern.
33. The dilution ventilation control system of claim 32 wherein
both of said supply and exhaust air volumes are increased when at
least one air contaminant exceeds a threshold level or
approximately matches a signal pattern.
34. The dilution ventilation control system of claim 32 wherein at
least one of said air contaminants exceeding said threshold level
or approximately matching a signal pattern is an output of a
photo-ionization detector TVOC sensor exceeding a predetermined
threshold level.
35. The dilution ventilation control system of claim 34 wherein
said photo-ionization detector TVOC sensor is calibrated with
isobutylene and wherein said predetermined threshold level is
between about 0.3 to 5.0 ppm.
36. The dilution ventilation control system of claim 1 wherein the
signal processing controller or the critical environment airflow
controller comprises a hysteresis function.
37. The dilution ventilation control system of claim 1 wherein the
signal processing controller or the critical environment airflow
controller fixes an airflow command signal for a predetermined
amount of time to increase at least one of said critical
environment's supply and exhaust air volumes.
38. The dilution ventilation control system of claim 1 wherein the
signal processing controller or the critical environment airflow
controller gradually adjusts said supply or exhaust air volumes
over a time period greater than fifteen seconds.
39. The dilution ventilation control system of claim 1 wherein the
signal processing controller or the critical environment airflow
controller fixes a limit on an amount to which said supply and
exhaust air volumes may be changed during a given time period.
40. The dilution ventilation control system of claim 39 wherein
said limit on said amount to which said air volumes may be changed
during a given time period is related to a change in at least one
of said air contaminants.
41. The dilution ventilation control system of claim 39 wherein
said limit on said amount to which said air volumes may be changed
is based on whether an increase in a value or a decrease in a value
of said supply or exhaust air volumes.
42. The dilution ventilation control system of claim 39 wherein the
size of said step change varies dependent on which of said air
contaminants caused the need for additional dilution
ventilation.
43. The dilution ventilation control system of claim 1 further
comprising a connection to an Internet system wherein information
about said critical environments is sent to a password protected
website on said Internet system.
44. The dilution ventilation control system of claim 1 wherein said
critical environment comprises a special exhaust device.
45. The dilution ventilation control system of claim 1 wherein said
facility monitoring system monitors at least one air contaminant at
a plurality of locations comprising a first location that is in
said one-pass critical environment and a second location to
generate a first and a second air contaminant measurement
respectively; and wherein said signal processing controller
subtracts either the second air contaminant measurement from the
first air contaminant measurement, or the first air contaminant
measurement from the second air contaminant measurement, to create
a differential air contaminant measurement to create said airflow
command signal.
46. The dilution ventilation control system of claim 45 wherein
said second air contaminant measurement is indicative of at least
one outside air condition.
47. The dilution ventilation control system of claim 45 wherein
said second air contaminant measurement is indicative of a
condition of said supply airflow of said critical environment.
48. The dilution ventilation control system of claim 45 wherein
said second different location is at least a portion of an interior
of a supply ductwork that is connected to said critical environment
to provide supply air into said critical environment.
49. The dilution ventilation control system of claim 45 wherein
said second air contaminant measurement is indicative of conditions
located proximate to said critical environment.
50. The dilution ventilation control system of claim 49 wherein
said second location is in communication with said critical
environment.
51. The dilution ventilation control system of claim 49 wherein
said second location is a corridor.
52. The dilution ventilation control system of claim 45 wherein
said airflow command signal varies a dilution ventilation portion
of said critical environment's supply and exhaust air volumes.
53. The dilution ventilation control system of claim 45 wherein
said airflow command signal varies an offset airflow of said
critical environment.
54. The dilution ventilation control system of claim 45 wherein
said facility monitoring system comprises a multipoint air sampling
system.
55. The dilution ventilation control system of claim 54 wherein
said second air contaminant measurement is indicative of one or
more outside air conditions.
56. The dilution ventilation control system of claim 45 wherein
said airflow command signal reduces said critical environment's
supply air volume when said first air contaminant measurement
exceeds a first threshold level and said second air contaminant
measurement exceeds a second threshold level.
57. The dilution ventilation control system of claim 56 wherein
said second air contaminant measurement is indicative of one or
more outside air conditions or one or more conditions within a
supply duct providing airflow into the critical environment.
58. The dilution ventilation control system of claim 45 wherein
said facility monitoring system monitors at least two different air
contaminants at a plurality of locations comprising a first
location that is said one-pass critical environment and a second
location to generate at least two first location and two second
location air contaminant measurements; and wherein said signal
processing controller subtracts each second location air
contaminant measurement from the corresponding first location air
contaminant measurement to generate at least a pair of differential
air contaminant measurement to generate said airflow command
signal.
59. The dilution ventilation control system of claim 1 wherein said
facility monitoring system monitors a plurality of different air
contaminants of said critical environment to generate first and
second air contaminant measurements; and wherein said signal
processing controller responds to said first and second air
contaminant measurements to at least partially generate said
airflow command signal.
60. The dilution ventilation control system of claim 59 wherein the
first and second air contaminant measurements are measured by a
TVOC sensor and a particle sensor.
61. The dilution ventilation control system of claim 59 wherein
said facility monitoring system is a multipoint air sampling
system.
62. The dilution ventilation control system of claim 59 wherein
said signal processing controller generates an airflow command
signal that changes value to increase at least one of said supply
and exhaust air volumes when at least one of said first air and
second contaminant measurements exceeds one or more predetermined
threshold levels or approximately matches predetermined signal
patterns.
63. The dilution ventilation control system of claim 59 wherein
said signal processing controller generates an airflow command
signal that changes value to increase at least one of said supply
and exhaust air volumes when both of said first air and second
contaminant measurements exceed one or more predetermined threshold
levels or approximately match predetermined signal patterns.
64. The dilution ventilation control system of claim 59 wherein
said signal processing controller generates an airflow command
signal that changes value to increase at least one of said supply
and exhaust air volumes when said first air contaminant measurement
exceeds a threshold level that is a function of said second air
contaminant measurement.
65. The dilution ventilation control system of claim 59 wherein
said signal processing controller generates an airflow command
signal that changes value to increase at least one of said supply
and exhaust air volumes when at least one of said first or second
air contaminant measurements exceeds a threshold level that is a
function of an occupancy level of said critical environment.
66. The dilution ventilation control system of claim 1 wherein said
facility monitoring system is a networked photonic sampling system
that senses at least one of said air contaminants of said critical
environment.
67. The dilution ventilation control system of claim 66 wherein at
least one of said air contaminants comprises one or more volatile
organic compounds.
68. The dilution ventilation control system of claim 66 wherein at
least one of said air contaminants comprises particles.
69. The dilution ventilation control system of claim 66 wherein
said airflow command signal varies a dilution ventilation portion
of said critical environment's supply and exhaust air volumes.
70. The dilution ventilation control system of claim 1 wherein the
facility monitoring system monitors at least three different air
contaminants of said critical environment to generate a first,
second and third air contaminant measurements; and said signal
processing controller responds to said first, second, and third air
contaminant measurements to at least partially generate said
airflow command signal.
71. The dilution ventilation control system of claim 1 wherein at
least one of said air contaminant sensors comprises a particle
sensor.
72. A method for varying the dilution ventilation airflow volume in
a one-pass, critical environment provided with a variable source of
supply airflow volume, which is completely exhausted from said
critical environment and from the building containing said critical
environment through one or more exhaust ducts, at least one of
which contains an airflow control device to vary an exhaust airflow
volume from said critical environment comprising: monitoring at
least one air contaminant of said critical environment by at least
one air contaminant sensor to create at least one air contaminant
measurement; creating an airflow command signal using at least one
of said air contaminant measurements; and controlling said critical
environment's supply and exhaust airflow volumes at least partially
using said airflow command signal.
73. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of: monitoring carbon dioxide levels of said
critical environment by at least one carbon dioxide sensor and;
wherein said step of creating an airflow command signal further
comprises using a measurement from said carbon dioxide sensor.
74. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein one or
more of said air contaminant sensors is shared and comprises a TVOC
sensor or a particle sensor.
75. The method of claim 74 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said TVOC
sensor is a photo-ionization detector TVOC sensor.
76. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said step
of monitoring at least one air contaminant comprises transporting
air samples from a plurality of locations comprising at least one
one-pass, critical environment to one or more shared air
contaminant sensors.
77. The method of claim 76 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the step
of transporting of air samples from a plurality of locations
utilizes a star configured multipoint air sampling system.
78. The method of claim 76 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the step
of transporting of air samples from a plurality of locations
utilizes a networked air sampling system.
79. The method of claim 76 for varying the dilution ventilation
airflow volume in one-pass, critical environments further comprises
the step of creating at least one virtual sensor signal from an air
contaminant measurement.
80. The method of claim 79 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein at least
one of said virtual sensor signals is in communication with a
building control system.
81. The method of claim 80 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein at least
one of said virtual sensor signals is in communication with a
building control system through a data communications means.
82. The method of claim 76 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising a step of sampling said air samples in a sequence that
is based on an output signal of the signal processing
controller.
83. The method of claim 82 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the
sampling sequence is based on an output signal of said signal
processing controller indicating a rapid rise in the amplitude of
an air contaminants above a trigger level.
84. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal varies a dilution ventilation portion of
said critical environment's supply and exhaust air volumes.
85. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal varies an offset airflow of said critical
environment.
86. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said step
of controlling said critical environment's supply and exhaust
airflow volumes at least partially uses an output from a sensor
located in said critical environment.
87. The method of claim 86 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
sensor located in said critical environment is an occupancy
sensor.
88. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments further comprises
the step of transporting air samples from a plurality of locations
comprising a location that is an air duct that provides airflow to
or from air one or more of said critical environments.
89. The method of claim 88 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein at least
one of said locations wherein at least one of said air samples is
indicative of the outside air conditions.
90. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal is a discontinuous airflow command
signal.
91. The method of claim 90 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
discontinuous airflow command signal is a two state signal.
92. The method of claim 90 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
discontinuous airflow command signal is a three state signal.
93. The method of claim 90 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
discontinuous airflow command signal is a multiple state
signal.
94. The method of claim 90 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal is a continuously variable command
signal.
95. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments, wherein said
airflow command signal increases said supply or exhaust air volumes
when an air contaminant measurement exceeds a threshold level or
approximately matches a signal pattern.
96. The method of claim 95 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the
threshold level can be changed automatically.
97. The method of claim 95 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein at least
one of said air contaminants exceeding a threshold level or
approximately matching a signal pattern is measured based on an
output from a photo-ionization detector TVOC sensor exceeding a
predetermined threshold level.
98. The method of claim 95 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
photo-ionization detector TVOC sensor is calibrated with
isobutylene and wherein said predetermined threshold value is
between about 0.3 to 5.0 ppm.
99. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein both of
said supply and exhaust air volumes are increased when at least one
air contaminant exceeds a threshold level or approximately matches
a signal pattern.
100. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said step
of controlling said critical environment's supply and exhaust
airflow volumes comprises increasing both of said supply and
exhaust air volumes when said airflow command signal commands a
greater airflow than any other airflow commands controlling said
supply and exhaust air volumes.
101. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal comprises a hysteresis function.
102. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal is fixed for a predetermined amount of time
to increase at least one of said critical environment's supply and
exhaust air volumes.
103. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal changes a value of said supply or exhaust
air volumes gradually over a time period greater than 15
seconds.
104. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein any
changes in a value of the airflow command signal are implemented
through a succession of smaller step changes in value.
105. The method of claim 104 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein a size of
one or more of said step changes in value is related to a size of a
change in value of said at least one of said air contaminants.
106. The method of claim 104 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the size
of said step change varies depending on whether a change in a value
of said supply or exhaust air volumes is an increase in value
versus a decrease in value.
107. The method of claim 104 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the size
of said step change varies depending on which of said air
contaminants caused a need for additional dilution ventilation.
108. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of providing a connection to an Internet system
wherein information about the critical environments is sent to a
website on said Internet.
109. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said step
of monitoring at least one air contaminant comprises monitoring a
first location, that is said one-pass critical environment, and a
second location to generate a first and a second air contaminant
measurement respectively; and further comprising the steps of,
subtracting either said second air contaminant measurement from
said first air contaminant measurement, or said first air
contaminant measurement from said second air contaminant
measurement, to generate a differential air contaminant
measurement; and generating said airflow command signal from said
differential air contaminant measurement.
110. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second air contaminant measurement is indicative of one or more
outside air conditions.
111. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second air contaminant measurement is indicative of a condition of
said supply airflow of said critical environment.
112. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second location is at least a portion of the interior of the supply
ductwork that is connected to said critical environment to provide
supply air into said critical environment.
113. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second air contaminant measurement is indicative of conditions
proximate to said critical environment.
114. The method of claim 113 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second location is in communication with the critical
environment.
115. The method of claim 113 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second location is a corridor.
116. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal varies a dilution ventilation portion of
said critical environment's supply and exhaust air volumes.
117. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal varies an offset airflow of said critical
environment.
118. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the steps of monitoring at least two different air
contaminants at each of a plurality of locations to generate a pair
of first location and second location air contaminant measurements;
subtracting said second location air contaminant measurements from
the corresponding first location air contaminant measurements to
generate a pair of differential air contaminant measurements; and
generating said airflow command signal from said pair of
differential air contaminant measurements.
119. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of transporting air samples from a plurality of
locations to at least one shared air contaminant sensor to generate
said first and second air contaminant measurements.
120. The method of claim 119 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second air contaminant measurement is indicative of one or more
outside air conditions or conditions within a supply duct providing
airflow into the critical environment.
121. The method of claim 109 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
airflow command signal at least partially reduces said critical
environment's supply airflow volume when at least said first air
contaminant measurement exceeds a first threshold level and said
second air contaminant measurement exceeds a second threshold
level.
122. The method of claim 121 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said
second air contaminant measurement is indicative of one or more
outside air conditions or conditions within a supply duct providing
airflow into the critical environment.
123. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein said step
of monitoring of at least one air contaminant comprises monitoring
a first air contaminant of said critical environment to generate a
first air contaminant measurement; and further comprising the steps
of monitoring at least a second different air contaminant of said
critical environment to create a second air contaminant
measurement; and generating said airflow command signal using at
least said first and second air contaminant measurements.
124. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the first
air contaminant and the second air contaminant measurement are
measured by a TVOC sensor.
125. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments of claim 123
further comprising the steps of transporting air samples from a
plurality of locations comprising at least one of said one-pass,
critical environments to a plurality of shared air contaminant
sensors; and monitoring a plurality of air contaminants of said
critical environment by the shared air contaminant sensors to
generate a plurality of different air contaminant measurements.
126. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of varying said airflow command signal to
increase at least one of said supply and exhaust air volumes when
an air contaminant measurement exceeds a predetermined threshold
level or approximately matches a signal pattern.
127. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of varying said airflow command signal to
increase at least one of said supply and exhaust air volumes when
both of said first and second air contaminant measurements exceed
predetermined threshold levels or approximately match signal
patterns.
128. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of varying said airflow command signal to
increase at least one of said supply and exhaust air volumes when
said first air contaminant measurement exceeds a threshold level
that is a function of said second air contaminant measurement.
129. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the step of varying said airflow command signal to
increase at least one of said supply and exhaust air volumes when
at least one of said first or second air contaminant measurements
exceeds a threshold level that is a function of a occupancy level
of said critical environment.
130. The method of claim 123 for varying the dilution ventilation
airflow volume in one-pass, critical environments wherein the first
air contaminant and the second air contaminant measurement are
measured by a particle sensor.
131. The method of claim 72 for varying the dilution ventilation
airflow volume in one-pass, critical environments further
comprising the steps of monitoring a first, second and third
different air contaminants of said critical environment to create a
first, second and third air contaminant measurements; and
generating said airflow command signal using at least said first,
second and third air contaminant measurements.
Description
CROSS-REFERENCE
[0001] This is a continuation-in-part of U.S. Provisional Patent
Application Ser. No 60/660,245 filed on Mar. 10, 2005.
FIELD OF THE INVENTION
[0002] This invention relates to systems for controlling
ventilation to dilute contaminants within critical environments or
spaces such as laboratories and vivariums which utilize a
"one-pass" ventilation strategy in which the airflow out of each
environment is entirely exhausted without a recirculated air
component, and more particularly, to systems and methods for
varying the flows of supply and exhaust air into and from these
environments for the purposes of controlling the dilution of air
contaminants based on changes in the presence of these contaminants
as sensed by a facility monitoring system.
BACKGROUND OF THE INVENTION
[0003] This invention relates to the dynamic control of dilution
ventilation in one-pass, critical environments. Critical
environments in the context of this invention relate to spaces,
areas or rooms in which potentially hazardous materials may be used
that could become airborne and impact in some way the health of
individuals operating within the space. Examples of such spaces
include but are not limited to laboratories where chemicals or
biological materials are used as well as vivariums or animal
research facilities where animals are housed for research purposes.
Other types of applicable areas include but are not limited to:
clean rooms, pharmaceutical processing areas, bio-safety
facilities, and medical containment and isolation facilities.
Furthermore, critical environments may be further narrowed down to
those which are strictly one-pass environments, which in the
context of this invention refers to those spaces which use one-pass
air, in other words no air from the space is returned or
recirculated to an air handler or fan system for use again within
the building. As such all air introduced to within the space either
from a supply system, or as transfer air from another space, is
exhausted typically through some sort of exhaust system which takes
the room air and exhausts it from the building typically controlled
by some sort of room exhaust or special exhaust air flow control
device. Specifically, these rooms have no return air grills or
return airflow control devices. Control of the room's airflow is
thus accomplished through one or more exhaust airflow control
devices designated for the space plus one or more supply airflow
control devices that although typically are designated for the
space, may also be somewhat remote from the room if some of the air
from those devices enters the space as transfer air from another
space that is provided with supply airflow via a separate air flow
control device. Furthermore, a flow of air that is drawn from or
supplied to a space or environment may be expressed as a volume of
air per unit time, for example, in terms of cubic feet per minute
(cfm).
[0004] Dilution ventilation as used in the context of this
invention refers to the use of airflow supplied to the room either
directly or as transfer air that dilutes or reduces the
concentration of possible contaminants in the air of the room.
Although capture and containment of hazardous vapors is the safest
approach to handling hazardous materials, dilution ventilation
provides an important backup or secondary form of protection for
the critical environment in case the primary or containment control
device malfunctions, or else an accident or spill occurs, or the
occupants of the space use unsafe practices that introduce
contaminants into the air of the room. Dilution ventilation is also
sometimes referred to or defined as the minimum level of airflow
allowed in the room, or as the airflow corresponding to the
critical environment's minimum air change requirement typically
expressed as a minimum air changes per hour (ACH) for the
space.
[0005] As the price of oil, natural gas and other fuel sources has
increased over the years, there has been interest in reducing the
amount of outside air that is used by buildings to save energy,
while still maintaining good indoor environmental quality within
those facilities. In the context of this invention outside air is
defined as the ambient air outside of the building housing the
critical environment that maybe drawn into the building to provide
some measure of fresh air ventilation. Since laboratory and
vivarium facilities typically use 100% outside air these facilities
use extremely large amounts of energy compared to other types of
facilities such as office buildings that are able to use return or
recirculated air. The purpose of the present invention is to
significantly reduce the energy consumption of a critical
environment utilizing one-pass or 100% exhaust air for dilution and
potentially other purposes while also enhancing the safety of these
environments.
[0006] As mentioned earlier, one example of a critical environment
in which a one-pass, dilution ventilation system may be employed is
a laboratory. A laboratory generally is a facility that is designed
to permit the safe use of various chemicals, biologicals, toxic
compounds and/or other potentially harmful substances for research
or other purposes. The laboratory may be equipped with one or more
"special exhaust devices" that are designed to exhaust air from the
lab to an outside environment to protect lab users from potentially
dangerous exposure to harmful substances. For example, a laboratory
may include one or more of the following special exhaust devices
such as laboratory fume hoods, canopy hoods, glove boxes, or
non-recirculating biological safety cabinets, in which potentially
harmful substances may be regularly handled. Additionally, exhaust
trunks sometimes referred to as snorkel exhausts are special
exhaust devices that may be used to exhaust air containing
potentially harmful substances from a particular area on a bench
top or from an analytical instrument thereby providing local
containment and protection. Additionally, a laboratory may include
one or more exhausted storage cabinets that are special exhaust
devices that are used to store potentially hazardous substances and
function to contain harmful fumes or vapors that might leak from
the stored substances. The described laboratory environment may be
used for many purposes, such as research, teaching, manufacturing
or production, quality control, pilot or scale up, or other
functions. Additionally the laboratory may contain many types of
areas adjacent to or beyond the research areas such as support
rooms, equipment rooms, corridors, offices and other types of rooms
found in a laboratory building that may also be one-pass
environments with all the air from the spaces exhausted to outside
the facility.
[0007] Another example of a critical environment in which a
one-pass dilution ventilation system may be employed is a vivarium
as mentioned earlier. A vivarium is generally a facility used to
house animals for research purposes. These animals which can
include rats, mice, rabbits, larger mammals, and even aquatic life
such as fish have many environmental requirements. In addition to
proper temperature control and lighting, it is important to use
containment and or dilution ventilation to reduce and exhaust
odors, animal dander, particles, gases from the animal's metabolic
functions, and potentially toxic gases from the animal holding and
other rooms that are part of these facilities. In addition to
protecting the animals, the reduction and elimination of these
contaminants in the air is important to the health and safety of
the animal care and research staff who use these facilities. In
particular, the exposure of these people to animal allergens, such
as rat urine protein (RUP) or mice urine protein (MUP), that is
often carried in the air on particulates can over time sensitize
the animal care workers and researchers, and create allergic
reactions in these individuals from the animals via contaminated
air in the facility. The vivarium may also have special exhaust
devices, for example the animal cage racks that are often used to
house rats and mice for example have cages with filter membrane
tops and are also ventilated. In particular, these racks may be
directly exhausted into a general exhaust duct via a constant,
2-state, or variable air volume valve or other flow control device
like a damper-based system.
[0008] Additionally, some vivarium or animal facility rooms may
contain biosafety cabinets that may be exhausted, snorkel exhausts
or laboratory fume hoods. Vivariums may also have many different
functions similar to the lab room functions mentioned above and
similarly as mentioned above may have many types of rooms such as
support rooms, surgery, examination rooms, cage wash area,
corridors, "clean" corridors, "dirty" corridors, offices, and other
rooms that are part of the animal or vivarium facility that do not
house animals yet still are one-pass environments.
[0009] In view of the foregoing, conventional ventilation processes
in a laboratory facility, vivarium, or potentially other similar or
related critical environments where dilution ventilation is
employed, generally involve supplying 100% fresh outdoor air to the
environment in the form of supply air ducted directly into the
space or supply air that is supplied to other nearby spaces and
then passes into the environment as transfer air or as a constant
source of offset air. It should be obvious to those who are
experienced with building ventilation system technology that this
ducted supply air is usually provided via an air handler that
contains a fan to move the air, but also will usually include a
method for heating, cooling, and filtering the air. Offset airflow
is specifically defined as a typically fixed difference in airflow
between the ducted supply into the space and the ducted exhausted
airflow from the space. Depending on whether the supply is greater
than or less than the total exhaust airflow from the space
determines whether the environment is at a positive or negative
pressure respectively with respect to an adjacent room or corridor.
As an example for labs, typically the supply air is controlled to
be less than the exhaust to ensure that the lab is at a negative
pressure with respect to the corridor. In the context of this
invention, corridor is defined as a passageway that may be adjacent
to and is in communication with a plurality of rooms or critical
environments.
[0010] There are three factors that may be typically used to
determine the level of supply and exhaust airflow into the critical
environment. The first of these factors is the space thermal load.
Typically the supply air into the space is conditioned at a
temperature such as 55 degrees F. and used for cooling the
environment. The heat sources with in the lab can be solar load,
lights, people and the so-called plug loads from the heat generated
by equipment and instrumentation within the lab. As these loads
increase the cool supply air must be increased to maintain a given
temperature set point such as 72 degrees Fahrenheit. Occasionally,
the lab may be cooled using methods other than the supply air such
as from a cooled ceiling or floor or from a local fan coil unit
that pulls air from the room, passing this air through cooling
coils (typically chilled water coils), and passes it back into the
room. In these latter two cases the control of the environment's
supply and exhaust airflow would be unaffected by the thermal load
factor. For purposes of this invention a single pass environment
would not be altered from a pressurization standpoint by adding the
aforementioned fan coil and, therefore, would be viewed as being a
single pass environment even though it may be connected to a
locally recirculating fan coil or other device such as a ductless
fume hood, glove box, or other device that locally recirculates air
from said environment while having no net influence on the offset
airflow to the environment.
[0011] A second factor that can determine the environment's
required supply and exhaust airflow is the exhaust airflow from any
special exhaust devices as described earlier as well as the
associated make up air needed to match the exhausted airflow. These
sources of exhaust air may be fixed sources such as from storage
cabinets or biosafety cabinets, two-state (high/low) sources or air
or fully variable sources such as with variable air volume
laboratory fume hoods. Alternatively, the space or environment may
have no special exhaust devices and thus this factor will not
affect the airflows of the space.
[0012] The third and final factor affecting the environment's
required supply and exhaust airflow is the airflow requirements for
dilution ventilation. This requirement is typically expressed as a
certain number of air changes per hour (ACH) for the space such as
6 air changes per hour of total exhaust (including special exhaust
airflow) or total supply (including offset and transfer) airflow.
This number of air changes per hour can then be converted into a
specific airflow rate for a given volume space. For example if an
environment is 20 feet long by 25 feet wide and 9 feet high, the
total volume of the space is 4500 cubic feet. Thus 6 air changes an
hour would mean that in 60 minutes the entire volume of 4500 cubic
feet would be exchanged 6 times, or equivalently there would be one
air change in 10 minutes (60 minutes/6 ACH=10 minutes per air
change). For the volume of 4500 cubic feet to be exchanged in 10
minutes would require a total room supply or exhaust flow of 450
cfm (4500 cubic feet/10 minutes per air change=450 cfm). Typical
industry accepted required flows for dilution ventilation range
from 6 to 12 air changes per hour.
[0013] Furthermore, this amount of air changes per hour of airflow
is typically a fixed level that is set irrespective of the actual
quality of the room air, even though the air exhausted from the lab
environment often is clean and safe. Additionally, due to
simplicity and costs, some portions of the lab or vivarium
environment served by the ventilation system, such as storage areas
and support areas, or even offices where there may be no hoods,
animals, or active research are also ventilated with one-pass air
at these levels, even though the possibility of contaminants being
present in these areas is less likely. Accordingly, the minimum
fixed air changes requirements for 100% outside air in conventional
laboratory, vivarium, or other dilution ventilation systems often
results in wasted resources (i.e., fresh outdoor air) and
unnecessarily excessive operating costs as well as high up front
capital costs for sufficient sizing of the building's heating,
ventilating and air conditioning system also referred to as the
HVAC system.
[0014] The typical approach used to integrate the three factors, or
requirements mentioned above, into a single flow requirement for
total exhaust or supply is simply to take the highest of the three
requirements. If constant volume airflow devices are used then they
must be set for the highest of the peak requirements of each the
three factors. If variable volume airflow control devices are used,
then the environment airflow can vary based on the highest of the
actual requirements such as the variation in thermal load.
Traditionally, in many one-pass, critical environments, the
dominant factor that has been the controlling factor has been
either the thermal load or the requirements of the special exhaust
devices such as laboratory fume hoods.
[0015] As such there have been many inventions and technologies
developed to safely vary the environment's airflow to save energy
based on either or both of varying airflow to meet the actual
thermal load requirements, or varying the airflow through the
special exhaust devices. The latter has often been done through the
use of variable air volume laboratory fume hoods; such as those
described in U.S. Pat. Nos. 4,706,553; 4,893,551. and 5,240,455;
since fume hoods have often been the dominant driver behind
laboratory airflows. More complex airflow controls involving the
sensing of air contaminants in critical environments that would
typically be dominated by thermal loads have also been developed to
safely vary and recirculate air from critical environments, such as
described in U.S. Pat. Nos. 6,609,967 and 6,790,136 through the
addition of a return airflow control device to each critical
environment to return and reuse clean air in an air handler serving
multiple lab rooms.
[0016] In the last five to ten years, there have two important
trends that have affected the airflow levels in labs. First, the
numbers of laboratory fume hoods and related special exhaust
devices has decreased. This is partly related to the increased use
of computers to model chemical reactions vs. lab experimentation,
as well as the use of smaller amounts of chemicals in research.
Additionally, more life sciences labs that tend to have less fume
hoods are being built today vs. the traditional chemistry lab with
many fume hoods. Furthermore, many labs today are built with
variable air volume laboratory fume hood control systems to reduce
the amount of exhaust and make up air related to the fume hood. As
a result the lab ventilation requirements related to special
exhaust or fume hood make up air have been reduced significantly,
so that in many labs it is not the driving force determining the
airflow or ventilation in the lab.
[0017] Second, thermal loads in labs have also dropped as more
energy efficient technologies are being used in labs. The
efficiency and waste heat from lighting for example has dropped
significantly as has the power used by lab instrumentation.
Although in the early 90's the amount of lab instrumentation
increased significantly, over time this equipment has become
smaller and more energy efficient. Refrigerators and freezers have
in many cases dropped their power consumption by two-thirds, plus
LCD displays and laptops have replaced desktop computers and large
energy hungry CRT monitors. Many recent studies show this result,
such as a study from the Lawrence Berkeley National Laboratory
mentioned in the September, 2005 issue of HPAC Engineering entitled
"Right-sizing Laboratory HVAC systems". This article demonstrates
that labs are often over designed for thermal loads that are 5 to
10 times more than what the lab environment will actually be used
for.
[0018] As a result of these two trends, the minimum or dilution
ventilation requirement has emerged as often the dominant and
controlling factor in laboratory airflow requirements. If this
level can, on average, be reduced it would save significant amounts
of energy in laboratories as well as allowing a smaller HVAC system
that would save first cost in the construction of the facility. As
a point of fact, the level of minimum air change or dilution
ventilation requirements are also usually set somewhat arbitrarily,
for example at levels of between 6 to 12 air changes per hour for a
laboratory or 10 to 20 ACH's for a vivarium.
[0019] Occasionally to save energy, this dilution rate is made a
two state flow reduced during unoccupied times to a set lower level
such as 4 ACH and then increased during occupied times to a higher
level such as 8 ACH. This control can occur by a set time schedule
control or through the use of an occupancy sensor such as those
commonly used to shut off lights. Although this approach can save
energy it has several safety problems that negate its prudent use.
For example, a spill or release of hazardous vapors can occur
during an unoccupied time increasing the level of contaminants in
the air above safe levels. If someone were to walk into the space
during this scheduled unoccupied time, they could be injured by the
higher level of contaminants in the air. Even with an occupancy
sensor or detector, when the individual walked into the room the
level of contaminants could be quite high, exposing the individual
until the system both detected their presence and more importantly
was able to adequately flush out the lab with the higher occupied
airflow which could take some time. Furthermore, occupancy
detectors can have problems with detecting people in a broken up
space with many barriers such as lab shelves and equipment between
the sensor and the occupants. They also need to constantly see
motion to operate and may fail to see someone quietly reading with
insufficient motion to trigger the higher safe airflow. If the flow
is dropped due to lack of sufficient motion, the occupant might not
notice the flow change and then even worse could possibly be
overcome by a higher level of contaminants in the lab.
SUMMARY OF THE INVENTION
[0020] It is therefore a primary object of this invention to
provide a system for controlling ventilation to dilute contaminants
within critical environments or spaces, such as laboratories and
vivariums which utilize a "one-pass" ventilation strategy in which
the airflow out of each environment is entirely exhausted without a
recirculated air component.
[0021] It is a further object of the invention to provide systems
and methods for varying the flows of supply and exhaust air into
and from these environments for the purposes of controlling the
dilution of air contaminants based on changes in the presence of
these contaminants as sensed by a facility monitoring system.
[0022] The systems and methods of the invention were developed
using a novel, improved approach, from both a safety and an energy
savings perspective over the prior art use of a time clock or
occupancy sensor, to vary minimum ventilation levels would be to
instead vary the amount of dilution ventilation airflow or
equivalently defined in the context of this invention, the air
change rate of a space, based on the level of an air contaminant in
the space as measured by a facility monitoring system. In the
context of this invention a facility monitoring system is defined
as a monitoring system that includes at least one air contaminant
sensor that measures at least one air contaminant of at least one
room, space, area or critical environment. Such a facility
monitoring system may involve the use of one or more individual,
local, wired or wireless sensors located in the space being
measured. It may also use remote or centralized air contaminant
sensors that are multiplexed or shared amongst a plurality of
spaces as is described in more detail later. Finally, a facility
monitoring system may use a combination of the previously mentioned
remote and local air contaminant sensors. As such these
facility-monitoring systems may be used to measure many different
air contaminants as well as potentially other characteristics of
the monitored space such as temperature, humidity, or differential
pressure with respect to some other space.
[0023] An air contaminant sensor in the context of this invention
refers to a sensor that converts the level of or information about
the presence of an air contaminant into either a continuously
varying or else discontinuous pneumatic, electronic, analog or
digital signal or else into a software or firmware variable
representing the level of or information about the presence of an
air contaminant in a given space. The air contaminant sensor may be
based on any of a variety of sensing technologies known to those
skilled in the art such as for example electrochemical, photonic or
optical, infrared absorption, photo-acoustic, polymer, variable
conductivity, flame ionization, photo-ionization, solid state,
mixed metal oxide, ion mobility, surface acoustic wave, or fiber
optic. The air contaminant sensor may be a wired or wireless sensor
type and be implemented with various types of physical hardware
such as for example micro-electro-mechanical system based (MEMS),
nanotechnology based, micro-system based, analog based, or digital
based. Additionally, an air contaminant sensor may sense for more
than one air contaminant, may include more than one air contaminant
sensor in one packaged device, or may sense for or include sensors
for other non-contaminant air parameters such as for example
temperature, pressure, or a measure of humidity. In the context of
this invention, air contaminants refers to certain chemical,
biological, or radiological composition elements or properties of
the air such as for example carbon monoxide (CO), particles of
various sizes, smoke, aerosols, TVOC's (Total Volatile Organic
Compounds), specific VOC's of interest, formaldehyde, NO, NOX, SOX,
SO.sub.2, nitrous oxide, methane, hydrocarbons, ammonia,
refrigerant gases, radon, ozone, radiation, biological and or
chemical terrorist agents, mold, other biologicals, and other
chemical characteristics of the air and contaminants of interest to
be sensed. Also, in the context of this invention the term air
contaminants specifically does not include or refer to such air
characteristics or parameters such as any measure of temperature,
carbon dioxide, or humidity such as for example any of the linked
measures of temperature and moisture or water vapor in the such as
relative humidity, absolute humidity, wet bulb temperature, dry
bulb temperature, dew point temperature, or grains of moisture per
pound of air. Additionally, in the context of this invention, air
contaminants also does not specifically include or refer to any
measure of airflow volume, velocity or pressure such as air volume
as may be indicated in units of cubic feet per minute of air or
other units, velocity pressure, air speed or velocity, static
pressure, differential pressure, or absolute pressure.
[0024] The air in modern laboratories is often quite clean such
that high air change rates are unnecessary except for example when
a spill happens; poor lab practices generate fumes, vapors or
contaminants in the lab outside the containment devices like fume
hoods; or when the containment devices work poorly leaking chemical
fumes into the space. Since the far majority of the time the lab
air is clean, the dilution ventilation airflow can be brought down
significantly the majority of the time to a level such as 2 to 4
ACH's vs 6 to 12 ACH's creating significant ventilation savings.
Additionally when a spill occurs, the system can increase the
dilution ventilation rate to a high level such as 12 to 15 ACH,
providing increased safety through a fast evacuation of the spilled
vapors from the lab.
[0025] Dynamic control of dilution ventilation based on monitoring
the quality of air with a facility monitoring system can be
accomplished with several different embodiments. Perhaps the
simplest approach to dynamically vary air change requirements in
one-pass, critical environments, such as labs or vivariums, would
be to use a single, broad based contaminant sensor such as a TVOC
or total volatile organic compound sensor located in each room or
airflow control zone that is to be controlled. This approach can
for example increase the dilution ventilation airflow requirements
when the contaminant sensor detects that contaminants are above a
given threshold level. When the contaminant level returns below the
given threshold level, the dilution ventilation airflow requirement
is brought back down to the minimum set point level. In all
conditions if the thermal load or special exhaust make-up airflow
requirements are above the required dilution ventilation flow
requirements, then these requirements will override and take
control of the room's airflow level in a high select form of
control.
[0026] There are several important issues to be taken into account
when implementing this type of one sensor per room/airflow control
zone approach to the dynamic control of dilution ventilation. First
of all, the selection and use of lower cost, typically metal oxide
type TVOC sensors may create problems due to the relatively high
drift and even poisoning and degradation that can often occur with
these types of sensors when they are exposed to certain airborne
contaminants that are likely to be found in labs, vivariums or
other environments where outside air is used to dilute airborne
contaminants. A preferred alternative would be to use a
higher-grade TVOC sensor such as for example a photo-ionization
detector (PID) style sensor. These sensors although typically more
expensive, are also more stable and much less apt to be compromised
by the gases they are detecting. Additionally, the use of a TVOC
sensor, even a PID type TVOC sensor, will not detect all
contaminants of concern in a lab. For example, there could be a
release of an aerosol, hazardous particles, or smoke from an out of
control reaction that needs to be rapidly evacuated from a lab.
Similarly, non-organic acid gases, for example, could be quite
harmful to a researcher but similarly will not be detected by a
TVOC sensor. Furthermore, there may be certain specific
contaminants that are of concern that would be beneficial to sense
such as formaldehyde or ammonia. Finally, depending on the allowed
minimum air change level, if a space may be heavily occupied, such
as with a teaching lab, CO.sup.2 monitoring may be needed as a
means of detecting heavy occupancy levels and increasing airflow to
meet outside air requirements and guidelines related solely to the
amount of people in the space such as to meet a typically used
guideline of 15 to 20 cfm of outside air per person. As such an
embodiment that can be used to deal with these issues would use
multiple sensors vs. just one sensor in one or more rooms or where
it is appropriate to detect some of these other contaminants to
provide safe operation of the system and potentially also to sense
CO.sup.2 for additional airflow control related to occupancy.
[0027] An exemplary embodiment of the current invention that
provides another solution to these issues and is both practical and
cost effective is the use of a multipoint air sampling system,
otherwise known as a multiplexed or shared sensor based facility
monitoring system, as the means to sense the quality and
cleanliness of the lab environment. Multipoint air sampling system
are defined for the purposes of this patent as specifically a
facility monitoring system that uses shared or multiplexed
sensor(s) consisting of either a single remote sensor or a set of
remotely located sensors that is used to monitor a plurality of
spaces, areas or rooms within a building, or outside adjacent to a
facility by transporting samples or packets of air from the
critical environment to be monitored to the at least one air
contaminant sensor.
[0028] For one class of these multipoint air sampling systems
specifically defined, in the context of this invention, as star
configured multipoint air sampling systems or just star configured
systems, multiple tubes may be used to bring air samples from
multiple locations to a centralized sensor(s). Centrally located
air switches and/or solenoid valves may be used in this approach to
sequentially switch the air from these locations through the
different tubes to the sensor to measure the air from the multiple
remote locations. Each location may be sensed for between 10
seconds or several minutes. Depending on how many locations are
sensed each space may be sensed on a periodic basis that could
range from 5 to 60 minutes. These star configured systems may be
called octopus-like systems or home run systems and may use
considerable amounts of tubing. An example of such a star
configured system is described in U.S. Pat. No. 6,241,950, which is
incorporated herein by reference. Other types of known air
monitoring systems include those that have been designed to monitor
refrigerants and other toxic gases, which also are star configured
systems. Additionally, these types of star configured systems have
been used to monitor particulates in multiple areas such as clean
room areas with a single particle counter.
[0029] Generally, these types of systems have not historically been
applied to general air quality measurement applications involving
multiple parameters such as TVOC's. Another multipoint air sampling
system defined in the context of this invention as a networked air
sampling system uses a central "backbone" tube with branches
extending to various locations forming a bus-configured or tree
like approach similar to the configuration of a data network. Air
solenoids are typically remotely located proximate to the multiple
sampling locations. The sampling time for each location like with
the star configured systems may vary from about 10 seconds to as
much as several minutes. A typical sampling time per location would
be about 30 seconds, so that with 30 locations sampled, each
location could be sampled every 15 minutes. Networked air sampling
systems can also include remote and/or multiple-location air
sampling through a tube or pipe for sampling locations in a
building, outdoor air or ambient sampling, and exhaust air stacks.
An exemplary networked air sampling system is described in U.S.
Pat. No. 6,125,710, which is incorporated herein by reference.
[0030] Finally another multiplexed form of facility monitoring
system that may be used to implement portions of this invention is
defined in the context of this invention as a networked photonic
sampling system that multiplexes packets of light vs. packets of
air and may incorporate either a star configured or network/bus
type of layout. The basic concept uses a central laser emitter and
a central laser detector that sends out and detects laser light
packets that are switched into rooms to be sensed by optical
switches. Optical fiber sensors, infrared absorption cells or
sensors, and other sensing techniques are located and used in the
sensed area to change the properties of the light due to the affect
of the environment. The light packet is then switched back to the
central detector where the effect of the environment on the light
properties is determined. A major benefit of the system is that the
sensors such as the fiber or open cell sensors are potentially
quite low in cost. The expensive part is the laser and detector
systems that are centralized. Like in the previous multipoint air
sampling systems, multiple affects on the light from particles,
gases and other contaminants, humidity, etc. can be done
simultaneously with central equipment and the telecom concept of
Wavelength Division Multiplexing which allows multiple wavelengths
and hence multiple signals to share the same fiber. A clear
advantage of this system is the ability to have a cycle time that
can be in ten's of milliseconds or less. This sampling system is
detailed in U.S. Pat. No. 6,252,689, entitled "Networked Photonic
Distribution System for Sensing Ambient Conditions" which is also
incorporated herein by reference.
[0031] The multipoint air sampling systems and networked photonic
sampling system which have been described heretofore and are
collectively referred to as sampling systems may be applied to
monitor a wide range of locations throughout a building, including
any kinds of rooms, hallways, lobbies, interstitial spaces,
penthouses, outdoor locations, and any number of locations within
ductwork, plenums, and air handlers. To provide control as well as
monitoring of these different spaces, virtual sensor signals can be
created that in the context of this invention refer to software or
firmware variables, or continuous analog or digital signals that
can be passed to other systems such as a building control or
laboratory airflow control system and are representative of the
state of a given space's air contaminant value. In effect these
signals are reflective of what a local sensor would read if it was
being used instead of the multipoint air sampling system or
networked photonic sampling system otherwise known collectively
again as sampling systems.
[0032] Another characteristic of these sampling systems is that
some characteristics or parameters of the air such as temperature
in particular, as well as some air contaminants such as potentially
ozone can not always be effectively measured from a remote location
with a shared sensor. Furthermore, other contaminants may be
accurately measured at a remote location with a shared sensor but,
for various reasons such as the need for more rapid sampling, may
be preferably sensed locally at one or more of the sensed
locations. In these situations, separate local sensors and either
distinct signal wires or a digital data communications network with
cable, optical fiber or wireless links can be used to connect these
local sensors such as temperature sensors to either the networked
air sampling system, star configured multipoint air sampling
system, networked photonic sampling system, or possibly a building
management system. These virtual sensor signals plus potentially
local sensor signals can be combined to create blended signals that
may be used advantageously for monitoring and or control purposes
as described in U.S. patent application entitled, "MULTIPOINT AIR
SAMPLING SYSTEM HAVING COMMON SENSORS TO PROVIDED BLENDED AIR
QUALITY PARAMETER INFORMATION FOR MONITORING AND BUILDING CONTROL"
and filed on Mar. 10, 2006, which is incorporated herein by
reference.
[0033] When the multipoint air sampling systems are used to sample
ductwork, plenums, air handlers or any other applications where
flowing air in a partially contained area such as a duct or pipe is
to be sampled and measured with a remote sensor, a tube or hollow
duct probe may be inserted into the duct or partially contained
space to withdraw a sample or else a hole can be made in the duct
and a sample drawn from the duct from a tube connected to the
opening in the duct wall. Additionally however, a separate
temperature or other parameter or contaminant sensing probe or
probes are needed to make whatever local sensor measurements are
desired from these ducts or partially enclosed areas. Multiple
separate probes for both sensing the flowing air stream and for
drawing air samples may be employed or a unique integrated sampling
probe that uses one probe for both local air characteristic
measurements and for air sampling may be used as described in the
U.S. patent application Ser. No. 11/312,164, entitled "DUCT PROBE
ASSEMBLY SYSTEM FOR MULTIPOINT AIR SAMPLING" which is incorporated
herein by reference.
[0034] Another embodiment of the current invention uses the virtual
signals from a multipoint air sampling system and or the signals
from local room or duct air contaminant sensors and combines them
via one or more of multiple approaches using a signal processing
controller to create a dilution ventilation command signal that in
the context of this invention is an airflow command signal that can
be used to vary at least partially the dilution ventilation airflow
or air change rate of a critical environment based on one or more
air contaminants.
[0035] For the purposes of this patent, an airflow command signal
is any pneumatic, electronic, analog or digital signal, or a
software of firmware variable that operates in a firmware or
software program running on a microprocessor or computer, that is
used by either the critical environment airflow controller or by
one of the room exhaust, special exhaust or supply airflow control
devices to at least partially vary or control one of the aspects of
or relationships between any one of the airflows moving into or
exiting the critical environment. This airflow command signal may
be of a continuously varying nature and is otherwise referred to
herein as a VAV or variable air volume command signal. Otherwise,
the airflow command signal may be a discontinuous airflow command
signal which in the context of this invention is defined as a
signal that may have only two levels or states and for the purposes
of this patent is referred to as a two state signal, or it may have
three levels or states and may thus be referred to in the context
of this invention as a three state signal. Alternatively, the
discontinuous airflow command signal may have multiple discrete
levels or states and as thus may be referred to herein as a
multiple state signal.
[0036] When multiple air contaminants are to be used by a
signal-processing controller to create a dilution ventilation
airflow command signal, particularly where each contaminant has a
different threshold of concern, each contaminant can be scaled to a
standard scale relative to that threshold. For example 2 volts in a
0 to 10 volt scale can represent the threshold at which point the
airflow begins to be increased with 10 volts representing maximum
flow. These individual signals can then be high selected so the
higher of these signals controls the dilution flow. Alternatively,
the signals can be summed together after they have been weighted in
a relative manner based on the severity of the health effects of
each sensed compound.
[0037] Another problem of concern with the dynamic control of
dilution ventilation based on the measurement of air contaminants
in a space is that if outdoor levels of a contaminant go high due
to re-entrainment of "dirty" exhaust flows, high outdoor dust
levels, traffic, etc, the system could be triggered by these levels
and increase the supply airflow into the rooms. This action would
actually make matters worse and would "latch" virtually all the
controlled spaces up at the high ventilation level. Since the
system capacity would have been likely not designed for each space
operating at maximum flow then, this event would call for a system
capacity that could not be achieved. This potentially could
compromise the airflow control throughout the building, reducing
flows, and thereby creating loss of capture with the special
exhaust devices as well as potentially compromising room
pressurization levels. A similar problem of exceeding system
capacity could also be achieved if for example the hallways of a
lab or vivarium are being mopped with a cleaner that gives off
VOC's. The floor cleaner fumes could be quickly pulled into many of
the negatively pressurized lab rooms thereby triggering many of the
lab spaces into a high flow level state, thereby creating a similar
capacity problem.
[0038] To prevent multiple spaces from going to high dilution
ventilation incorrectly due to a high outdoor level of
contaminants, another embodiment of the current invention describes
a means to vary the dilution ventilation of a space not on the
absolute value of a given contaminant, but instead on the
differential value of that air contaminant vs. either an outdoor
air value, a supply airflow value, or the value measured in an
adjacent or nearby space. In this manner the room does not
incorrectly increase the flow of a contaminated supply air stream,
when the contaminant sensed is not from inside the room. In a
related embodiment, if the absolute level of the room exceeds the
threshold value for action, yet the source of the contaminant is
from the supply of outside air, the supply air may be decreased.
For example, the supply air may be decreased by commanding a lower
dilution ventilation level and/or commanding an increased
temperature set-point, to reduce the thermal load requirements on
the supply volume.
[0039] For those critical environments where there is a concern
that a spill or contamination of the room could spread to other
rooms or for other reasons requiring increased containment or
protection, a further embodiment of the present invention could
increase the exhaust air and decrease the supply air of the
affected room or area to increase the negative pressure offset of
the contaminated room to increase the level of containment of that
space vs. other spaces. If a given room is believed to the source
of a potential contamination, then surrounding rooms could be
increased to a positive pressure to further isolate the
contaminant.
[0040] For the purposes of this patent a signal processing
controller as mentioned above refers to analog or digital
electronic circuitry, and or a microprocessor or computer running a
software or firmware program that uses at least information,
signals and or software or firmware variables from either
individual local sensors of air contaminants and or other air
characteristics such as temperature, humidity, air volumes, or
pressures plus virtual sensor signals, information and or software
or firmware variables from remote, centralized sensors of air
contaminants, and combines and processes this information in a
potential multitude of ways. As a result the signal processing
controller either creates airflow command signals for dilution
ventilation, offset air volumes, or other airflow commands to be
used by a critical environment airflow controller, and or create
signals or information that can be used by other control devices
such as a building control system for at least partially
controlling one or more critical environment airflows of supply,
room exhaust, special exhaust or offset airflow, and or is used for
some other control or monitoring function that is in some way
related to the control of one of the aforementioned critical
environment airflows.
[0041] In the context of this invention, a building control system
or building management system as mentioned above is defined as a
control system located in a building or facility that is used to
control one or more functions of the HVAC system in a building such
as for example control of space temperature, space relative
humidity, air handling unit airflows and operation, exhaust fan
flows, chiller operation, duct static pressures, building
pressurization, critical environment airflows. These systems often
integrate with or incorporate other building systems or subsystems
such as fire and security, card access, closed circuit TV
monitoring, smoke control systems, power monitoring, and critical
environment airflow control systems. Building control systems may
have pneumatic, electric, electronic, microprocessor, computer, or
web based controls using pneumatic, analog and or digital signal
inputs and outputs. These systems often have centralized monitoring
functions, centralized or local control capabilities, and may have
Internet or web based access. They may also be referred to as
building management systems (BMS), facility control systems or
facility management systems (FMS).
[0042] Finally, there may be improved or at least alternative
approaches to increasing ventilation in a lab that has a spill
event. For example is the door of the space to the corridor has
been left open, the slight negative pressure of the lab room vs.
the corridor may not be enough to prevent the spill vapors from
contaminating other adjacent areas. It may be better to
specifically have the system react in some other way to ensure that
the vapors are contained in the room with the spill.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Other objects, features and advantages will occur to those
skilled in the art from the following description of the preferred
embodiments and the accompanying drawings in which:
[0044] FIG. 1 is a schematic diagram of a preferred embodiment of
the system of the invention in which a plurality of one-pass,
critical environments are being monitored by a multipoint star
configured air sampling system.
[0045] FIG. 2 is a schematic diagram of a preferred embodiment of
the system of the invention in which a plurality of one-pass,
critical environments are being monitored by a multipoint networked
air sampling system.
[0046] FIG. 3 is a detailed schematic diagram of a preferred
embodiment of the system of the invention in a one-pass, critical
environment.
[0047] FIG. 4 is a schematic diagram of a portion of a preferred
embodiment of the signal processing logic of the invention that may
be used to create the dilution ventilation command signals.
[0048] FIG. 5 is a schematic diagram of an embodiment of the
critical environment airflow controls logic of the invention for a
one-pass, critical environment space including one or more special
exhaust sources.
[0049] FIG. 6 is a schematic diagram of an embodiment of the system
of the invention in which a plurality of one-pass, critical
environments are being monitored by one or more of individual local
sensors comprising one or more unique features.
[0050] FIGS. 7A and 7B are schematic diagrams of various
steady-state levels associated with air change rate control
sequences.
[0051] FIGS. 8A and 8B are diagrammed strategies for controlling
the air change rate in critical environments using a closed loop
system to provide dilution ventilation control by varying the air
change rate within a critical environment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND METHODS
[0052] FIGS. 1, 2 and 6 all show a typical set of monitored
critical environments or rooms 20A, 20B, and 20C that have doors
entering a corridor 10 that is also being monitored. Due to a
positive or negative pressurization of the critical environments,
an offset may exist between the critical environment space or area
and an adjacent space. An example of this is shown in FIGS. 1, 2
and 6 as offset airflow 21A, 21B, and 21C between the spaces 20A,
B, and C and corridor 10. Although the diagrams show three rooms
and a corridor, the present invention may be used with any
plurality of rooms or spaces including corridors or other adjacent
spaces that are also being monitored, such as for example, two or
more critical environments, or one corridor plus one or more
spaces. Note also that, although the critical environments shown in
the Figures are enclosed within walls, critical environments in the
context of this invention may also be a section or area of a room
having no walls or partitions around it. Thus, there may be
multiple critical environments within one physical room.
Alternatively, multiple physical rooms may also constitute one
critical environment or space. Typically, the critical environment
20 will also be an area that is fed by one or more supply airflow
control devices 51 plus one or more room exhaust devices 41 that
are being controlled by a critical environment airflow controller
30 as one airflow control zone. For the purposes of this patent a
critical environment airflow controller is an airflow control
apparatus that may be of analog or digital electronic design or may
be constructed using a microprocessor or computer running a
software-or firmware program that creates the airflow command
signals for one or more supply and or exhaust airflow control
devices possibly using information, signals and airflow commands
from other devices, systems or controllers. FIG. 5 shows one
embodiment of a critical environment airflow controller.
[0053] These sets of rooms in FIGS. 1, 2 and 6 are further
described as having a source of supply air from supply air ducts
50A, 50B, and 50C that may exit the room as room or general exhaust
air from room or general exhaust ducts 40 A, 40B, and 40C. Although
not shown in the figures, the corridor 10 often has a source of
supply air and possibly room exhaust as well. The supply ducts 50A,
B and C also contain airflow control devices 51A, B, and C which
supply air into the room or space through supply flow grill or
diffuser 52A, B, and C respectively. Additionally, the room exhaust
ducts 40A, B, and C contain room exhaust airflow control devices
41A, B, and C which control the amount of room or space air pulled
into the room exhaust duct through a room exhaust grill or vent
opening 42A, B, and C respectively.
[0054] FIGS. 1, 2, and 6 also show the presence of an outdoor air
intake 62 into the building through outside air duct 60. This duct
could be connected to or part of some type of an air handling unit
to pull in outside air into the building or may be a special duct
or outside air pickup location specifically used for or shared by
the air sampling systems 100 and 200 of FIGS. 1 and 2 respectively
or the air contaminant sensing system of FIG. 6.
[0055] An airflow control device as used in the context of this
invention, such as the supply and room exhaust airflow control
devices 51 and 41 respectively or the special exhaust airflow
control device 71 shown in FIG. 3, is defined as any device known
to those skilled in the art of airflow control for controlling air
flow volume and velocity through a duct. For example, they can be
constant volume, two state, multiple state, or variable air volume
(VAV) boxes or terminals such as manufactured by Titus, Metal Aire,
Enviro-Tec, or others. These devices use a damper or throttling
device of some type such as a single round, square, or rectangular
blade damper, a multiple blade damper, a set of pneumatic bladders
that can be used to seal off an opening, or any other type of
throttling device that can be used to seal off a duct, that is
connected to a pneumatic, electric, or electronic actuator that is
controlled by a pneumatic, electronic, digital, or microprocessor
based controller which typically also relies on feedback of flow
from a flow sensor for closed loop control of the duct's air
volume. These flow sensors can be of various types known to those
skilled in the art, such as those based on single or multiple
velocity pressure sensors, hot wire, heated thermistor,
microelectronic flow sensor, etc. Alternatively, another type of
flow control device that is commonly used is an airflow control
valve that typically has a venturi shaped body with a spring loaded
cone that moves through the venturi shaped throat of the device to
provide inherent, pressure independent control of volume, such as
manufactured by Phoenix Controls or others. These valves typically
have pneumatic, electric, or electronic actuation to provide
constant volume, two-state, multiple state, or variable air volume
control. These devices often have large turndown or flow ranges
that make them very appropriate for dynamic control of dilution
ventilation that can have wide flow ranges to achieve optimum
energy savings and safety. Finally, another example of an airflow
control device may be some form of a single or multiple blade
damper or other type of throttling device that is located either in
an air handling unit or a duct serving one or more areas or
potentially multiple critical environments which further includes
one of the airflow measuring devices aforementioned or similar
airflow measuring devices that are adapted using a grid of sensors
or sensing holes for example to measure the airflow accurately
across a large cross sectional duct area.
[0056] Although not shown in FIGS. 1, 2, and 6 the critical
environments 20A, B, and C may also have one or more special
exhaust airflow devices as mentioned above which also pull air out
of the critical environments. An example of this is shown in FIG. 3
as special exhaust device 72, and special exhaust airflow control
device 71 which will be both explained in more detail later.
[0057] With reference to FIG. 1, this diagram refers to a preferred
embodiment of the present invention directed to dynamic control of
dilution ventilation in one-pass, critical environments using a
star configured multipoint air sampling system 100. Multipoint air
sampling system 100 could be a star configured multipoint air
sampling system with a structure like that described in U.S. Pat.
No. 6,241,950; U.S. Pat. No. 5,292,280; U.S. Pat. No. 5,267,897;
U.S. Pat. No. 5,293,771 or U.S. Pat. No. 5,246,668. It could also
be a refrigerant and toxic gas monitor adapted for this purpose
such as the Vulcain Inc. multipoint sample draw gas monitor model
number VASQN8X as can be seen on their website at
www.vulcaininc.com or a multiplexed particle counter such as the
Universal Manifold System and Controller made by Lighthouse
Worldwide Solutions, Inc., as can be seen at their website at
www.golighthouse.com, coupled with one of their particle counters
such as their model number Solair 3100 portable laser based
particle counter or an obscuration based particle sensor. It could
also be a star configured multipoint air sampling system like that
of the AlRxpert 7000 Multi-sensor, Multipoint Monitoring system
manufactured by AlRxpert Systems of Lexington, Mass., as can be
seen at their website at www.airexpert.com.
[0058] In FIG. 1, a set of solenoid valves 161 through 167 is part
of a multipoint air sampling system 100. Equivalently, these
solenoids 161 through 167 could be replaced with other switching
means such as SSS-48C Single Scanivalve System manufactured by the
Scanivalve Corporation of Liberty Lake, Wash. as can be seen on
their website, www.scanivalve.com, which uses a pneumatic selector
switch and stepper motor to connect one of many input ports to an
outlet port which can be connected to a sensor such as a pressure
sensor. The solenoid valves 161 through 167 are controlled to
switch in a sequence by control logic 110. This sequence may be a
simple sequential pattern of one solenoid after another, or varied
for example through programming to be one of potentially many
preset patterns, or it can have a pattern that can be interrupted
and changed to a new sequence by manual or remote command or by a
trigger event based on the values or signal pattern of one or
multiple sensed contaminants. This trigger event could be generated
from outside the multipoint air sampling system 100 or could be
created from the sensor information processed by signal processing
controller block 130.
[0059] The solenoid valves 161 through 167 are connected to
sampling locations 13, 23A, and 23C in the spaces as well as duct
sensing locations 43A, 43B, 53B, and 63 through tubing 14, 24A,
44A, 44B, 54B, 24C, and 64. In FIG. 1 for example, sampling
location 13 in corridor 10 is connected through tubing 14 to
solenoid 161. Area sensing locations 23A and C in rooms 20A and C
are connected through tubing 24A and C to solenoids 162 and 166
respectively. Room exhaust duct sampling locations 43A and B are
connected through tubing 44A and B to solenoids 163 and 164
respectively. Supply duct sampling location 53B is connected
through tubing 54B to solenoid 165. Finally outside air duct
sampling location 63 is connected through tubing 64 to solenoid
167. Alternatively, tubing 64 may be connected to some other
suitable location other than duct 60 to obtain outside air
samples.
[0060] The tubing mentioned above transports the air sample from
the sensing location to the solenoid of the multipoint air sampling
system 100. The tubing typically will have an inner diameter of one
eighth to one half an inch in diameter with a preferred inner
diameter of about one quarter inches. This tubing can be made of
standard plastic pneumatic tubing such as Dekoron.TM. low density
polyethylene (LDPE) plastic, Teflon, stainless steel, "Bev-A-Line
XX" tubing made by Thermoplastic Processes, Inc. of Stirling, N.J.,
or other suitable tubing materials known to those skilled in the
art. For superior performance in transporting both TVOC's and
particles however, a material that is both inert to VOC's with very
little adsorption and desorption as well as electrically conductive
to prevent static buildup is preferred such as flexible stainless
steel tubing. Other preferred materials and constructions are
described in U.S. patent application Ser. No. 10/948,767, filed on
Sep. 23, 2004 entitled, "TUBING FOR TRANSPORTING AIR SAMPLES IN AN
AIR MONITORING SYSTEM", as well as U.S. patent application Ser. No.
11/149,941 filed on Jun. 10, 2005, entitled, "AIR MONITORING SYSTEM
HAVING TUBING WITH AN ELECTRICALLY CONDUCTIVE INNER SURFACE FOR
TRANSPORTING AIR SAMPLES".
[0061] Additionally in FIG. 1, a vacuum pump 140 pulls air from the
sensing locations through the tubing into the solenoids 161 through
167 and into a manifold 190 connecting all the output ports of the
solenoids together and to the inlet of the shared sensors 120. The
outlet of the shared sensors 120 is connected to the vacuum pump by
tubing 141, whose construction is not critical and can be
inexpensive plastic tubing such as the Dekoron.TM. mentioned above
or other. The inner diameter of this tubing can be made similar to
the size of the tubing connecting to the inlets of the solenoid
valves or possibly larger for less pressure drop. The shared
sensors 120 can consist of one or more sensors to measure such air
characteristics as humidity, CO.sup.2, dewpoint temperature, and
differential static pressure., as well as air contaminants such as
for example, CO, particles, smoke, TVOC's, specific VOC's of
interest, formaldehyde, NO, NOX, SOX, nitrous oxide, ammonia,
refrigerant gases, radon, ozone, biological and or chemical
terrorist agents, mold, other biologicals, and other air
contaminants of interest to be sensed. These sensors may be
connected in series, in parallel or a combination of both.
[0062] The signal outputs of the shared sensors 120 are passed to
the signal processing controller block 130 of the multipoint air
sampling system 100. This block 130 also accepts other sensor
information from the sensor inputs block 150. This input block 150
accepts sensor signals or information from local room or duct
sensors if needed or desired rather than remote sensors. For
example, temperature cannot be sensed remotely, since the
temperature of the air will change as it moves through the tubing.
Additionally, some areas may need instantaneous sensing or the
input may not be a sensed contaminant of the air such as the state
of a room switch or an occupancy sensor. This is shown in Room 20A
where room sensor 25A, which could for example be a temperature
sensor, is connected to the sensor inputs block 150 through
electrical cable 26A. Additionally optional occupancy sensor 27A,
which may provide a digital high/low signal indicating the presence
of someone in the space, is connected to sensor inputs block 150
through cable 28A. The sensors and the sensor inputs block may
accept many signal forms such as analog or digital. Alternatively,
the sensor may have its own onboard microprocessor and communicate
with the sensor inputs block 150 through a data communications
protocol such as, for example, LonTalk by Echelon Corporation, or
an appropriate protocol outlined by ASHRAE's BACnet communications
standards, or virtually any other appropriate protocol, including
various proprietary protocols and other industry standard protocols
commonly used to provide data communications between devices within
a building environment. Typically, however, when digital data
communications are used to connect to discrete devices such as 25A,
and 27A, this is accomplished using a protocol operating over a
physical layer such as an EIA485 physical layer, on top of which a
suitable upper level protocol will be used. In such cases, for
example, cable 28A may be specified as a twisted shielded conductor
pair. Nevertheless the connections between sensors 25A and 27A and
inputs block 150, may be accomplished using any number of cable
types common to the building controls industry. Additionally, cable
28A may be omitted and the sensors 25A and 27A may communicate
wirelessly to inputs block 150.
[0063] The signal processing controller block 130 is used to
process the sensor information from the shared sensors to create
virtual sensor signals reflective of the environmental conditions
in the sensed locations. This information is added to the
information from any local room sensors such as 25A and 27A, and is
then used in a variety of possible ways. For example, this
information can be sent to building control system 180 for
monitoring and or control purposes through a digital networked
connection 181. The information interchange could be done using for
example, a BACnet protocol, Lonworks, XML data interchange or other
suitable interface information conversion. The physical connection
181 could be an Ethernet connection, EIA485 (also known as RS485)
connection or other type of digital data communications connection.
Another use of the data can be to send it through an internal and
or external local area or wide area network for monitoring at a
remote location. Additionally, the data can pass directly, or
through a local area network, phone network or other suitable
connecting means 171 to connect to the Internet or a dedicated
network from which a website or other suitable means can be used to
remotely access, display, and analyze the data from the multipoint
air sampling system 100.
[0064] Most importantly, signal processing controller block 130 can
also provide the control signals 31 and 32 used by the critical
environment airflow controller 30 which in FIG. 1 is shown as block
30A, B, and C and dilution ventilation command signals 31A, B, and
C plus room offset command signal 32A. Control signal 31 is used to
dynamically vary the minimum air change rate or dilution
ventilation level of critical environment 20A, 20B, and 20C. The
control signal 32 is used to individually, or in combination, vary
the offset airflow 21A, B, and C of critical environments 20A, B,
and C both in magnitude and polarity or direction (positive to the
corridor or negative). Also, given the flexible nature of the
electronics associated with critical environment controller 30,
part or all of the functions performed by signal processing
controller 130 may be performed within controller 30, which can be
a programmable device. In this case, signals 31 and 32 may at least
in part be created within controller 30.
[0065] Referring to dilution ventilation command signals 31, the
signal processing controller block 130 can produce these signals,
or portions or all of the control functions can be produced by the
building control system 180, as is shown for example in FIG. 2,
using sensor information from the shared sensors 220 in FIG. 2 and
or the local room sensors 25A and occupancy sensors 27A. Further,
it should be clear that signal processing controller 130 of FIG. 1,
signal processing controller 210 of FIG. 2, or signal processing
controller 420 of FIG. 6 need not be physically packaged within
blocks 100, 200, or 400 respectively and that it's possible to
implement signal processing controllers 130, 210 or 420 as either
standalone modules, or to integrate them with some other portion
within FIGS. 1, 2 or 6, such as, for example, room sensor 25A.
There are several different control approaches for signal 31 that
can be implemented by the signal processing controller block 130 of
FIG. 1 as well as by the signal processing controller blocks 210 or
420 as shown in FIG. 2 or 6 respectively, or by the building
control system 180. These control approaches have two important
components. One component refers to the type of control approach
such as two state, three or multiple states, continuously variable
control, or methods involving a combination of both discontinuous
and continuous control functions. The other refers to how multiple
sensor signals are combined to generate a control signal. Note
however, that multiple signals are not required to dynamically vary
the dilution ventilation. One signal may be used alone, such as a
photo-ionization detector (PID) TVOC sensor that picks up a broad
range of chemical compounds, to generate the control signal. Many
types of PID TVOC sensors exist and are known to those skilled in
the art of TVOC sensing. Examples of one type of a PID TVOC sensor
are the RAEGuard PID, the ppbRAE Plus or the MiniRAE 2000 all
manufactured by Rae Systems of San Jose, Calif.
[0066] One embodiment of the control approach for dilution
ventilation command signal 31 is a two state control approach
whereby ventilation signal 31 is maintained at it's minimum level,
for example at a dilution ventilation value corresponding to, for
example, 2 or 4 ACH (or some other appropriate lower value
depending on what's suitable for the environment being monitored),
unless a trigger event occurs that could consist of a threshold or
trigger value being exceeded by the sensor signal. As mentioned
before if the sensor signal consists of just one contaminant, a
simple threshold or trigger value (corresponding to the value of
the sensed contaminant at which some action is to be taken) can be
defined. Alternatively, the trigger could consist of the signal
matching in some way a specified signal pattern such as a rapid
increase in level even though a specified threshold level was not
achieved. The trigger event could also consist of a combination of
one or more sets of threshold values and signal pattern pairs, any
one of which could constitute a trigger event.
[0067] If multiple sensor contaminants are being employed such as
from the shared sensors 120 and or a local room sensors 25A, the
trigger event could be defined as any one of the employed sensor
signals exceeding a threshold value, matching a signal pattern, or
meeting the conditions of one of potentially multiple sets of
threshold level and signal pattern pairs. Each sensor signal would
most likely have a different threshold value level and or signal
pattern that corresponds to an appropriate value for the sensed
contaminant based on accepted levels of that signal related to one
or a combination of health, comfort or other criteria of importance
for that sensed contaminant. For example, a PID TVOC sensor would
likely have a threshold level of about 0.5 to 2 PPM. A level in
this range senses many materials below their OSHA TLV (Threshold
Limit Value) while still not generating many false alarms by
staying above normal levels of less harmful materials such as
alcohol vapors. If a particle counter measuring in the range of 0.3
to 2.5 microns is used a level can be set that would not normally
be exceeded such as in the range of 1.0 to 5 million particles per
cubic feet, yet still pick up the evolution of smoke or some type
of aerosol release into the lab room. The specific level could be
set based on the level of filtration to the space, i.e. the more
the filtration, the lower the level that could be used. Other
sensors such as a carbon monoxide, ammonia, nitrous oxide, ozone,
or other toxic gas sensor can be set directly for the TLV of the
compound or for a lower level that would not normally be reached in
typical operation.
[0068] Alternatively, a triggering condition could consist of a
combination of two or more sensed air contaminants each reaching or
exceeding a given level for that compound or meeting some signal
pattern condition. For example, individually, a moderate level of
fine particles such as 1.5 million particles per cubic feet, a
moderate level of TVOC's such as 0.5 PPM, or a moderate level of
temperature excursion to above 85 degrees might in themselves not
trigger a need for increased dilution ventilation. However, the
combination of all three contaminants meeting the preceding
conditions could indicate a small lab fire or explosion that would
definitely require an increased level of dilution ventilation.
[0069] A further implementation of a trigger condition involving
multiple sensed contaminants could be an additive trigger
condition. A good example of this relates to exposure to hazardous
materials. OSHA indicates that the effective TLV of a mixture of
gases can be computed by adding the fractions of each individual
compound's level vs. it's TLV to get the fraction of the combined
mixture against the combined TLV. For example, if the system
detects that carbon monoxide is at 65% of the threshold limit value
and that sulfur dioxide is sensed to be at 70% of its TLV value
then although individually neither compound would trigger the
system the combination of the two would be at 135% of the combined
TLV and as such would constitute a trigger condition. To implement
this approach each sensed contaminant of interest would be
individually scaled and then added together and a threshold trigger
set for the summed result.
[0070] Another variation on how a trigger condition can be set up
is to have the trigger condition vary or be changed based on some
other contaminant. For example, a trigger condition could be varied
based on occupancy, if no one is in the space, the trigger
conditions for some contaminants might be raised slightly. The
trigger level could then be lowered when some one is detected or
determined in some way to be in the space through, for example,
occupancy sensor 27A in Room 20A, a card access system, or other
means such as the detection of changes in CO2 in the space. There
could also be manual local or remote override changes to the
trigger levels, based on for example, an increased or decreased
concern about the contaminants in the lab. Alternatively, the
levels could be changed automatically by the signal processing
controller 130, 210, 530, or 420 of FIG. 1, 2, 4, or 6
respectively, some other system such as the building automation or
building control system 180, or a critical environment airflow
control system.
[0071] Finally, any number of different logical or Boolean
combinations of sensed contaminant values or sensor signal pattern
conditions acting on any number of sensed contaminants affected by
any other set of conditions or acted upon by other systems can be
used to trigger a need for increased dilution ventilation by
increasing dilution ventilation command 31.
[0072] There are a vast number of control techniques that may be
used to generate command 31 in order to vary the amount of
ventilation within the monitored critical environment 20 in order
to dilute the sensed contaminant sufficiently to prevent the
concentration of the airborne contaminant from exceeding a specific
level. Any method that one may use, from a standpoint of control
logic or algorithm, whether it be an open or closed loop strategy
involving continuous or discontinuous control functions, fuzzy
logic, proportional-integral-derivative functions, feed-forward
functions, adaptive control, or other techniques known to those
skilled in the art of control system design, are considered to be
aspects of this invention.
[0073] FIG. 7A illustrates one possible scenario of steady-state
levels associated with command 31 when signal processing controller
130 is configured to provide a two-state control function such that
command 31 is increased to an enhanced dilution mode level from a
normal level or ACH (air changes per hour) value when a sensed
contaminant from critical environment 20 transitions above an
established trigger value. Conversely, when the value of the sensed
contaminant transitions from a level that's above the trigger value
to one below that value, command 31 will drop back to its normal
steady state ACH value. FIG. 7A makes no reference to the time
response of command 31 as it transitions from the normal ACH value
to the Enhanced Dilution mode and vice versa, as this is a function
of the particular control technique used to make such a transition
while ensuring that stability is maintained within the system. As
an embodiment of this invention the two-state approach of FIG. 7A
can be acceptable for use in many applications. However, in some
cases the system stability realized with the simple switching
mechanism depicted by FIG. 7A will benefit by including provisions
to prevent command 31 from oscillating.
[0074] As an embodiment of this invention, when command 31 is
transitioned from the normal ACH value (3-4 ACH, for example) to
the enhanced dilution mode (10-15 ACH, for example), command 31
will be latched or become fixed at that higher value, so that
following the transition if the measured contaminant drops below
the triggered value the air change rate will remain high. Such an
approach may be accompanied by some form of notification mechanism
from the Building Control System 180, or the sampling system 100,
300, 400, or via the internet connection 171, or from the air flow
controller 30 or some other component of the system that airflow
controller 30 connects to, which will alert maintenance personnel
or other staff that the trigger value has been exceeded so that
signal processing controller may be manually reset.
[0075] As an alternate embodiment, instead of latching command 31
when the value of the sensed contaminant exceeds an established
trigger value, one may apply a hysteresis function as shown in FIG.
7B which depicts another scenario of steady-state levels associated
with command 31, in which two different triggers or transition
points are provided (input low trigger and input high trigger).
Here the input high trigger is used when the command 31 is at a
level corresponding to the normal ACH value, while the input low
trigger is used when the command 31 is at a level corresponding to
the enhanced dilution mode.
[0076] An exemplary type of control approach for dilution
ventilation command signals 31 is a three state control approach.
Unlike the previously mentioned control approach, which had two
output levels such as a high level, typically for a purge, and a
low normal operating level, this approach has three output levels.
A typical application for these three levels would be the same two
levels mentioned previously with an intermediate level added that
is not for spills (an extreme transgression in the levels of a
sensed contaminant) but for controlling more moderate levels of
sensed contaminants that are desired to be lowered. For example, if
a level of between 1 PPM and 10 PPM from the TVOC detector is
sensed, the system would increment up a moderate level, say from a
minimum level of 3 ACH to a level of 6 ACH'S. However if the TVOC
detector sensed levels above 10 PPM, then the system would go into
a purge mode with perhaps 10 to 15 ACH's of dilution ventilation.
This approach limits energy consumption for moderate contaminant
levels and reduces the chance that if multiple rooms are at this
moderate level, that the total system airflow capacity of the
building will be exceeded by too many rooms being commanded to
maximum air change rate (ACH) value. Another benefit of a three or
other multiple level approach (or of a VAV approach as well) is
that it lessens the chance of realizing an unstable condition where
the room airflow can vary up and down due to a steady release of
contaminants that alternately is purged to a low value and then
slowly builds back up as the system alternately increases and
overshoots and then decreases and undershoots the desired dilution
airflow command level by an amount that exceeds what is required
for a stable operating condition.
[0077] The three state control approach can be extended beyond
three output states to any number of output states for dilution
ventilation command signals 31 to provide different levels of
dilution ventilation for a space. Finally any of the approaches to
use multiple sensed signals such as from the shared sensors 120 and
or a local room sensors 25A can as mentioned previously for the two
state approach, also be used for the three or other multiple state
control approaches.
[0078] An exemplary type of control approach for dilution
ventilation command signals 31 is a variable air volume or VAV
approach. In this approach, once the sensed contaminant signals
reach some trigger level or match some signal pattern, the dilution
ventilation command signal 31 can increase in a continuous manner
from a minimum level which would match the minimum state output of
the two or multiple state approach, all the way up to a maximum
level that would correspond to the maximum level of the two state
or multiple state approach. This effectively "infinite state"
approach would as mentioned with the previous control approaches
work with one or more sensed signals such as from the shared
sensors 120 and or a local room sensors 25A that could be combined
in any manner. One difference with this approach, however, is the
need for a "trigger" signal that has a continuous output that is
related to the command signal 31. This trigger signal can be formed
from one or a plurality of sensed signals such as from the shared
sensors 120 and or a local room sensor 25A as has been described
previously.
[0079] A linear or non linear relationship can be established
between this trigger signal and the command signal 31. For example
with a linear relationship an offset and simple scale or gain
factor can be used as well as a minimum and maximum clamp so that
as the trigger signal increases above the minimum command signal
value, the command signal 31 will increase as well until it hits
the maximum allowed command signal value. One of the reasons to use
a VAV approach is to create a closed loop control of the IEQ within
the monitored space so as to prevent an oscillating control pattern
that might be generated in some situations by a two state approach.
With the VAV approach an increased ventilation level could be
maintained between the minimum and maximum command signal 31 levels
without an oscillating command level, particularly where there is a
roughly constant level of contaminant emission. This approach could
be used to regulate the level of an air contaminant such as a TVOC,
particulate, or other at a certain setpoint rather than drive it to
a minimum level that could prove to be costly in terms of the
energy expense of running at high ventilation for extended periods.
This approach could be appropriate when the contaminant is not a
particularly hazardous one and can be set to be maintained at a
level that would not create a health impact such as particles.
[0080] Alternatively this VAV approach could be used for another
purpose with CO.sup.2 levels being sensed and used to set a given
minimum ventilation rate related to the occupancy or number of
people in the space such as given amount of outside air or cfm per
person to meet certain building codes and guidelines such as those
referred to in ASHRAE standard 62-2004 versus to control to a given
contaminant level. This can be done since there is a fixed
relationship between the level of CO.sup.2 in a space compared to
the amount of people in that space divided by the amount of outside
air introduced into the space. This type of control is sometimes
referred to as demand control ventilation and has been used in
office environments to allow outside air rates in facilities that
use recirculated or return air to approximately track occupancy
levels to a level such as for example 15 to 20 cfm per person. In
this control approach CO.sup.2 is used as a proxy for directly
measuring the cfm per person ventilation level due to the fixed
amount of CO.sup.2 exhaled by people, approximately 0.01 CFM per
person for a person doing light office work, providing a means to
effectively measure the number of people in a space divided by the
outside air introduced into that space.
[0081] In a VAV contaminant control approach where the contaminant
is controlled to a set point value, alternatively, instead of only
one signal, multiple of air contaminant signals may be combined or
added, using methods similar to those mentioned earlier, to
generate a single mixed or blended contaminant signal that can then
itself be controlled to a setpoint value.
[0082] FIGS. 8A and 8B show another embodiment which is a
generalized view of a closed loop system 900 used to provide
dilution ventilation control by varying the air change rate within
a critical environment, such as 20, in a continuous (or VAV)
fashion within prescribed limits in order to prevent the level of a
sensed contaminant, such as TVOC's for example, from exceeding a
prescribed value. Here, sensor feedback 908 is subtracted from
contaminant set point 901, which represents the level of the sensed
contaminant that system 900 is to control to, in order to (by error
stage 902) create error signal 914. Error signal 914 is acted upon
by control block 903 in order to create a term that is bounded by
Min ACH Clamp block 904 and Max ACH clamp 905 in order to yield
command 31, which is the command to air flow block 906, which is
composed of air flow controller 30 and the exhaust and supply flow
(42 and 52) that it controls. Also depicted in FIG. 8A is block
907, which represents the dilution characteristics of the critical
environment. For those who are familiar with the art of control
system design, 907 represents the transfer characteristics of the
environment which in this case defines how the air change rate of
the environment under control relates to the value of the sensed
contaminant 908. Here, error stage 902, reverse acting control
block 903, Min ACH Clamp 904, and Max ACH clamp 905 may be
implemented within signal processing controller 130, or within
Building Control System 180.
[0083] Control block 903 may be implemented using any of a large
number of control strategies known to those who are skilled in the
art of control system design and may as an example include any
combination of proportional control, proportional-integral control,
proportional-integral-derivative control, feed forward techniques,
adaptive and predictive control, and fuzzy logic strategies. One of
the essential elements of control block 903 is that it provide the
necessary reverse acting and level-shifting functions so that it
may properly act upon error signal 914 (given the subtractive logic
shown for error stage 902) in order to create a command term 31
which will yield an increase in the critical environment's air
change rate at least for the condition where the sensor feedback
908 exceeds the contaminant set point 901. (Alternatively, the
logic of 902 could be altered so that 901 is subtracted for 908.)
As an example, contaminant setpoint 901 may be set to 1.5 ppm and
the sensed contaminant may be, for example, TVOC's (using, for
example a photo-ionization detector--or PID sensor--). Control
block 903 will be configured so that when sensor feedback 908 is
less than setpoint 901 the output of 903 will be less than or equal
to the minimum clamp value established by minimum ACH clamp block
904. 904 is a "high-select" block in that it will compare the value
of the output of 903 to some minimum clamp value (4 ACH, for
example) and present the larger of the two values to the next block
905. For example, if the output of 903 is 2 ACH and the minimum
clamp value set in 904 is 4 ACH, the output of 904 will be 4 ACH.
The output of 904 is presented to Max ACH clamp 905 which provides
a "low-select" function in that it will compare the value of the
output of 904 to a prescribed "max clamp" value (12 ACH, for
example) and output the smaller of the two to air flow block 906.
The way the system 900 works is that if there is some sudden
increase in the level of the sensed contaminant (due to a spill in
a laboratory, for example) above the contaminant setpoint 901 (set
to 1.5 ppm TVOC's for example) the control block will (within the
limitations of max clamp 905 set to 12 ACH, for example) increase
command 31 to the value necessary to limit the TVOC concentration
within the controlled environment to 1.5 ppm. In practice, set
point 901 can be set to a value less than the TLV for the
contaminant to be sensed to insure that sustained concentrations
will be limited to a steady-state value that is safe.
Alternatively, contaminant set point 901 may have a dynamic value
that adjusts based on the persistence of the contaminant monitored
by 908.
[0084] FIG. 8B illustrates an alternate embodiment of system 900
that provides the same control functions as FIG. 8A, but for any
number "n" of contaminants. With this approach, a dedicated error
stage 902 and control function block 903 are provided for each
sensed contaminant (1 through "n"), with the nth sensed
contaminant's set point shown as signal 909 going to error stage
910 which has an output 915 that is processed by function block
912. The outputs from each control block, such as from control
blocks 903 to 912, are presented to high select block 913, which
passes the largest of the control terms from the control blocks to
airflow block 906 as command signal 31. Using this approach, one
can provide dilution ventilation control to an environment such as
20 based on a number of contaminants, such as TVOC's, particles,
and a host of other contaminants with individual setpoints such as
901 to 909 for each monitored contaminant.
[0085] An implementation of a portion of the signal processing
logic of the signal processing controller block 130 in FIG. 1, or
of block 210 in FIG. 2 is shown in signal processing controller
block 530 in FIG. 4. In this diagram the control functions can be
implemented in analog or digital logic or be implemented with
computer software or a firmware program or any combination of
these. In FIG. 4, shared sensors 520 create one or a multiple of
output signals or variables shown for example in the diagram as
sensor signals 525, 526, and 527 representing the outputs of
individual sensors CO2, CO, and TVOC's respectively. Although FIG.
4 illustrates the use of these three sensors, any number or type of
sensors can be used. Since the sensors are being multiplexed with
the air samples from multiple rooms, three in this example, the
individual or "virtual" sensor signals for a given room
corresponding to, as mentioned previously, a sensor signal or
represented software variable for a given air contaminant in that
room or area must be de-multiplexed from the signal stream of that
contaminant. This is done within signal processing controller 530
by the de-multiplexers 531, 532 and 533 that de-multiplex the CO2,
CO, and TVOC sensor signals respectively using the control signals
511 from the control logic block 510. Block 510 corresponds to
control logic block 110 in FIG. 1 as well as part of signal
processing controller block 210 and part of control logic block
310A, B, and C in FIG. 2. The output of the de-multiplexing blocks
531, 532, and 533 are individual or "virtual" sensor signals or
software variables that represent the sensed contaminants or other
air characteristics or air quality parameters for rooms 20A, B and
C. For example, signals 522A, B and C represent the signals or
variables for the sensed CO2 levels in rooms 20A, 20B and 20C,
respectively.
[0086] These virtual sensor signals will typically have a value
representing the last de-multiplexed value that will be held
constant at that level until the next sampling of the corresponding
location for that signal. At this point the signal will change
value to equal the new de-multiplexed value. This transition of
state from one de-multiplexed value to the next de-multiplexed
value can occur either as a rapid or approximately step change in
signal or it may occur gradually in a ramped manner lasting from
several seconds in time up to many minutes depending on the desired
properties of the virtual signal, what is being controlled with
that signal, and how often the location is being sampled. A
preferred approach would be to have a gradual change of value
occurring over between 5 and 60 seconds.
[0087] If we again focus on the variables for Room 20A, then the
signals for CO2, CO, and TVOC are 522A, 523A, and 524A
respectively. As mentioned previously these individual or virtual
sensor signals 522A, 523A, and 524A can then be modified with an
offset and scale factor block 534A, 535A, and 536A respectively as
needed or some other control function can then be applied. These
modified signals from blocks 534A, 535A, and 536A are then acted
upon by function block 537A. This is the block that may add these
signals together, take the higher of the signals, apply threshold
value or signal pattern trigger functions to the signals
individually or as a group, or apply some other approach to combine
or use these signals as mentioned previously. The result of block
537A after it has applied appropriate trigger criteria, some form
of non-linear or linear scale and offset criteria, control loop
gain fluction, or some other control or Boolean logic is to create
a two state, three or multiple state, or a VAV dilution ventilation
command signal. Finally, this command signal or control variable
may then be outputted to a building control system or to another
system as either a digital signal or variable such as signal 538A
or as an airflow command signal or software variable such as the
dilution ventilation airflow command signal 31A created by output
block 540A and used as an input to room 20A's critical environments
airflow control block 30A.
[0088] One other function that may be implemented within Function
block 537A is a time delay or ramp function. For example, when a
threshold value is exceeded, then the output of function block 537A
which will become ventilation command signal 31A could be increased
to it's maximum or purge value that might correspond for example to
a room air change level of between 10 to 16 ACH's. This increase in
value can occur instantly or may be commanded to be a gradual ramp
by function block 537A. Such a ramp or slowly increasing signal
could occur over the span of a minute or more. This might be done
so as to not make an objectionably rapid increase in the room's
flow level or cause problems with the control system trying to keep
up with a rapidly changing signal that could cause a pressurization
problem if the supply and exhaust control devices can not keep up
with the changing signal. Similarly, when the ventilation command
signal is meant to drop from a higher level such as 10 ACH down to
a lower or minimum level such as 4 ACH, the function block 537A
could create a slow ramp that gradually decreases the output signal
31A over some period of time such as one minute or more.
[0089] Similarly these increasing or decreasing ramps or gradual
changes in level could be made linear, with constantly increasing
or decreasing rates or made non-linear such as with an
exponentially changing rate so the ramp could start faster and
gradually slow down or conversely start slowly and gradually
increase its rate of change in value until the signal hits it final
value. These ramps could also be at different rates based on
whether the signal is increasing or decreasing. For example, it may
be advantageous to rapidly increase the dilution ventilation of a
room by rapidly increasing the dilution ventilation command 31 if a
spill or large increase in the contaminant level in the room is
detected. However, it may also be helpful to have a slow ramp
downward; perhaps taking 5 to 15 minutes to gradually come down in
dilution ventilation flow to make sure that the contaminant is
removed even to a level below the threshold of detection.
[0090] In an alternative to ramping the changing flow over a large
signal range, it may, for the same reasons mentioned above, be
desirable to change not just the rate of change of the dilution
ventilation command 31 created by the signal, processing block 530
and function block 537A within it, but also the amount of the step
change possible based on a change in the sensed air contaminants
such as from the shared de-multiplexed sensor signals 522A, 523A,
and or 524A. In other words, rather than allow a full slew from the
minimum dilution rate to the maximum dilution rate from one air
sample measurement, it may be desirable to limit the maximum step
change in dilution ventilation airflow. For example a maximum step
change size could be set for an increase in airflow representing
four ACHs in a possible range from a minimum of four ACH to a
maximum of sixteen ACH. With the maximum step size set for example
for four ACH, it would take three successive air samples to have
air contaminant values in excess of the trigger values to boost the
dilution command 31 from the minimum to it's maximum value.
Similarly, if the maximum reduction was also limited to a flow rate
equal to four AC it would take three successive measurements of the
critical environment's air contaminants to be below the trigger
value for the dilution command level to drop from a level
corresponding to sixteen ACHs down to four ACH.
[0091] In a manner similar to the ramp approach mentioned above,
the increasing and decreasing step heights may be of different
sizes. For example, to respond quickly to a spill there may be no
limit or a larger limit for an upward or increasing change in
dilution ventilation command 31. However, to ensure a large amount
of dilution to very low levels and reduce the possibility of an
oscillation if the source is not a spill, but a continuous
emission, it may be advantageous to have a smaller decreasing step
change size to hold the dilution ventilation at a higher level for
longer periods so it takes several air sample cycles to fully
reduce the ventilation level to its minimum level.
[0092] Another means to set the step heights or possibly the ramp
rates is based on the level of detected contaminants or their rate
of change. If a large value of contaminant and or a rapid rise in
its level is detected since the last sample or recent samples, it
may be advantageous to use different step change heights or ramp
rates. For example in a spill, where there is a sudden increase to
a large contaminant value, it may be prudent to immediately index
the dilution command 31 to its maximum value. Smaller or more
gradual increases in value could be set for smaller steps. On the
other hand a sharp downward increase might not change the downward
step level in order to keep the ventilation higher to better clean
the air. Alternatively, for energy saving reasons and or if there
happens to be many brief upward excursions of contaminant levels
that may not be hazardous, it may be more beneficial, if the
contaminant level has just rapidly dropped to below the trigger
level to quickly drop the ventilation command 31 to its minimum
level. As such, it may also be beneficial to have different step or
output characteristics associated with each air contaminant. As a
result, the output control characteristics would be different based
on which air contaminant(s) triggered the need for more dilution
ventilation.
[0093] Output signals of the signal processing controller block 530
may also be used to change the sampling sequence based on the
detection of a spill or a level of contaminant that is of interest
to more closely observe. In this alternate approach the sequencing
of air samples into the shared sensors from the critical
environments 20 may be altered through signal processing controller
block output signal 512 that is used by control logic block 510 to
modify the sampling sequence on a potentially temporary basis
during the period of a detected event of interest in a particular
space 20. Based on seeing the control signal or software variable
512 increase in value to some higher trigger level or exhibit some
signal pattern such as a rapid rise in amplitude, the control logic
block 510 might increase the frequency of the air sampling of the
space where the event was detected. Alternatively or additionally,
the areas around the affected space may be quickly sampled next or
sampled at a higher frequency as well to look for a spread of the
contaminant to other spaces. In the context of this invention a
rapid rise in amplitude can be defined as a sudden increase in
value to a level such as many times larger than the normal trigger
level in less than 5 minutes such as that seen due to a spill of a
volatile organic compound.
[0094] This change in sampling or control sequence can be
implemented with the sampling system of either FIG. 1 or FIG. 2. If
the latter system was being used, the detection of the event would
be most likely carried out by the signal processing controller
block 210 and the change in sequencing carried out by control logic
blocks 310A, 310B, 310C and 310D.
[0095] Another change in control sequence that could be implemented
if an event of some type is detected in a space or several spaces
would be to change the sampling sequence by adding air sampling of
several spaces at once to measure a mixed sample of several rooms.
This could be implemented for example, by turning on one or more
solenoids at once to gather a mixed sample of affected areas or of
multiple areas nearby the affected area to rapidly look for
potential spillage into other areas. This would be implemented in
the same manner as mentioned above but would involve turning on
multiple solenoid valves such as for example solenoids 161, 162,
263, and 164 in FIG. 1 or solenoids 361A, 362A, 363A, and 361B in
FIG. 2.
[0096] With reference to FIG. 2, this diagram refers to another
preferred embodiment of the present invention directed to dynamic
control of dilution ventilation in one-pass, critical environments
using a networked air sampling system such as one similar to that
described in U.S. Pat. No. 6,125,710. This sampling system has many
of the functions and is similar to the system indicated in FIG. 1
with the main difference being that the solenoid switches and some
of the controls are distributed throughout the building vs. being
located in one central unit. As a result, central sampling unit 100
shown in FIG. 1 is effectively replaced by sensor and control unit
200, along with distributed air and data routers 300A, 300B, 300C,
and 300D. The control of the sequencing of the system and the
signal processing functions are handled by signal processing
controller block 210. This block 210 carries out the functions of
blocks 510 and 530 in FIG. 4 that have been described previously.
The shared sensor block 220 carries out the same function as block
520 of FIG. 4 and block 120 of FIG. 1.
[0097] Blocks 300A, B, C and D are air and data routers that house
the solenoid valves 361A, 362A, 363A, 361B, 362B, 361C and 361D as
well as potentially some analog or digital input and output
capabilities that are contained in Input/Output blocks 320A and
320B. As an example, air sampling location 23A is connected via
tubing or air transport conduit 24A to solenoid 362A that is part
of air and data router 300A. This tubing or air transport media 24A
along with 44A, 14, 44B, 54B, 24C and 64 was described earlier
except that the air transport conduit may also have associated with
it some additional electrical conductors for the purpose of adding
networked data communication, low voltage power, signal wires and
other potential functions as described in U.S. patent application
Ser. No. 10/948,767, filed on Sep. 23, 2004 entitled, "TUBING FOR
TRANSPORTING AIR SAMPLES IN AN AIR MONITORING SYSTEM", as well as
U.S. patent application Ser. No. 11/149,941 filed on Jun. 10, 2005
and entitled, "AIR MONITORING SYSTEM HAVING TUBING WITH AN
ELECTRICALLY CONDUCTIVE INNER SURFACE FOR TRANSPORTING AIR
SAMPLES". Adding these conductors enables local sensors to be
conveniently and cost effectively added to the system.
[0098] For example, sampling location 23A, as well as the other
sampling locations 43A, 43B, 53B, 24C and 63, could also contain a
local temperature sensor to sense the room or duct temperature. The
signal from this temperature sensor or from other sensors such as
humidity, or other air characteristics can be sent to the air data
router 300 as a digital data communications signal though a data
communication cable such as a twisted pair, twisted shielded pair,
fiber optic cable or other digital data communications media.
Alternatively, the sensor information could be sent to the router
300 via an analog signal through one or more signal conductors as
an analog voltage or current signal. This analog signal can then be
converted to a digital signal by the I/O block 320A or 320B in the
router 300A or 300B respectively.
[0099] These I/O blocks 320A and 320B can also monitor other air
contaminants or signal inputs that are not associated with an
air-sampling inlet yet would have a data communications cable,
analog signal cable or other connection to the I/O block. An
example of these sensors is Room Sensor 25A which could be a
temperature sensor, an air contaminant sensor or other type of
sensor such as a light, differential pressure, air velocity or
other building sensor, as well as the occupancy sensor 27B,
occupancy switch 28C, or emergency exhaust switch 81. Of the latter
sensors or room switches, an occupancy sensor is defined in the
context of this invention as a sensor that can detect the presence
of people in a space through infra red energy, motion, card access,
or other means, whereas an occupancy switch is defined in the
context of this invention as a room switch such as a manually
operated light switch or other type of room switch operated by the
occupant when they enter or leave the space. A room switch in the
context of this invention is defined as some type of switch that
may be for example electrical, mechanical, photonic, or pneumatic
that is located in or near the critical environment that can be
manually operated to signal a change in state to a system connected
to it. An emergency exhaust switch is defined as a room switch such
as an electrical wall switch that can be thrown or actuated by the
occupant when an emergency event has happened such as a fire, spill
or explosion. The emergency exhaust switch may affect some outcome
such as to provide maximum dilution ventilation to the space and or
potentially provide a containment action by increasing the negative
offset of the space or it may be for monitoring only. This room
switch as well as some others may for convenience of sharing wiring
be located in the same room location and possibly in the same
enclosure as the air sampling pickup. Other types of room switches
or sensors could also be connected to the I/O blocks 320 of the air
and data routers 300.
[0100] Within the air data routers 300, the output of multiple
solenoid valves can be manifolded together with manifold 390A and
B. These manifolds plus the outputs of individual solenoid valves
such as 361C in air and data router 300C or solenoid 361D in router
300D are connected together with tubing or air transport conduit
202 to transport air samples to shared sensors 220 in the
multipoint air sampling unit 200 as moved by vacuum source 140. The
control of the air and data routers as well as the communication of
digital sensed air characteristic and contaminant data from the I/O
blocks within the routers or from the local sensors in the spaces
back to the multipoint air sampling unit 200 is through data
communications cable 201. The air transport media 202 can be
constructed using the same materials mentioned previously for
tubing 24A and other connections from the spaces 20 to the routers
300. The data communications cable 201 can be made with any
commonly used data communications media such as twisted pair,
shielded twisted pair, fiber optics cable or other. Additionally in
a preferred embodiment the air transport media 202 and the data
communications media 201 can be combined into one structured cable
as was described for the connections between the rooms 20 and the
routers 300.
[0101] As in FIG. 1 the multipoint air sampling unit 200 also
connects to the Internet 170 to send information about the critical
environments to a password protected website for review by the
occupants or facility personnel. Again as in FIG. 1 the multipoint
sampling unit 200 can also interface to and send data back and
forth through data communications media 181 with the facility's
building control or management system 180. This can be done
directly or through one of many interface protocols such as BacNet,
Lon by Echelon, XML, OPC, or others.
[0102] In addition to the air and data routers 300 that can accept
sensed input signals from the spaces 20 and provide signal outputs
31 and 32 to help control the rooms 20, the building control system
180 can also be used to accept various sensor input signals such as
29C from occupancy switch 28C and signal 82 from emergency exhaust
switch 81. This information can be used by the building control
system directly for control and also communicated back to the
multipoint air sampling system 200. The building control system 180
can also provide control signals to help control the airflow in
rooms 20 as shown by signals 31C, and 32C to the critical
environments airflow control block 30C using sensor information
from the multiplexed air sampling system 100 or 200 and potentially
locally sensed signals, room switch information, as well as other
building information.
[0103] FIG. 3 illustrates a more detailed diagram of one of the
critical spaces and some of the airflow control and feedback
devices and signals used therein. In addition to the components
that have been described previously, this diagram also shows the
room exhaust airflow sensing and control device or devices 41 and
room exhaust airflow control signal 47 as well as room exhaust
feedback signal 48. Also included is supply airflow sensing and
control device or devices 51 and supply airflow control signal 57
and supply airflow feedback signal 58. A new device that has been
shown is local temperature sensor 91 that communicates through
cable 92 to a temperature controller 90. This temperature
controller could be part of building control system 180, a
stand-alone system, or part of a separate system that controls the
airflow in a critical environment. Such a control system that
includes for example special exhaust, room exhaust, and supply
airflow controller devices 71, 41, and 51 respectively of FIG. 3 as
well as the critical environment airflow controller 30 and controls
at least room pressurization by maintaining either a given room
pressure or volume offset is referred to in the context of this
invention as a critical environment airflow control system which
may also in some cases be referred to as a laboratory airflow
control system. The purpose of temperature controller 90 is to
provide temperature control which can include sending a thermal
load or temperature command 93 to the critical environment airflow
controller 30 to increase or decrease the supply airflow into space
20. The temperature control 90 may also control a reheat coil to
increase the temperature of the supply air fed into the space 20 or
perimeter heating coils in space 20 for further means of
temperature control.
[0104] Another element not shown in FIGS. 1, 2, and 6 is the
addition of a special exhaust airflow control and sensing device
71. This control device is connected to a special exhaust duct 70.
Special exhaust device 72 could be one of many special exhaust
devices such as a laboratory fume hood, snorkel exhaust, canopy
hood, chemical storage cabinet, bio-safety cabinet, animal cage
exhaust, or other device that exhausts air from the critical
environment. Typically the flow of these devices is either fixed,
two state or variable based on some aspect of the device. For
example the flow through a laboratory fume hood can be made
variable and proportional to the size of the fume hood sash opening
to maintain a constant face velocity. This type of control can be
seen in FIG. 3 where the special exhaust device 72 controls the
special exhaust airflow control device 71 through airflow control
signal 77. The special exhaust feedback or sensed airflow signal 78
is sent to the airflow controller block 30 along with potentially
one or more other special exhaust air flow feedback signals
illustrated for example by feedback signal 88.
[0105] FIG. 5 is an exemplary embodiment of the control diagram for
the critical environment airflow controller 30. The supply airflow
within a one-pass critical environment space is set by the higher
of either the makeup air required by the space's special exhaust
flows, the room's supply airflow requirement to meet the
temperature command or the requirements for dilution ventilation in
the space. This is implemented as shown in FIG. 5 by first summing
any and all special exhaust feedback signals such as flow signals
78 and 88 by summing block 33. This totalized special flow exhaust
feedback signal is then provided as one input into the high select
signal comparator 34. Block 34 acts to take the highest of the
three signals provided to it, passing which ever of the three
signals is highest at any given time. The next input into high
select block 34 is the temperature command 93 for varying supply
flow which is then scaled and offset as needed in scaling block 38
to put it on the same scale factor as the other two airflow command
signals inputs, such as certain number of cfm per volt for an
analog voltage signal or scaled directly into a given set of units
such as cfm or liters per second for a software or firmware
variable representing airflow. The third signal is the dilution
ventilation command signal 31 which is generated with the
assistance of the multipoint air sampling system, the discrete
local sensor system of FIG. 6, or the building control system 180
and is again scaled and offset as needed by scaling block 39 to put
this command on the same scale factor as the other signals.
[0106] The command 57 for the supply airflow control device 51 is
further shown created by taking the output of the high select
comparator block 34 and subtracting offset signal 32 from it by
subtraction block 37. The room offset airflow command 32 could be a
fixed offset such as 10% of the maximum supply or exhaust cfm, or
it could be a signal that varies in a two state, multi-state, or
VAV fashion. The purpose of this offset airflow is to create a
typically slight negative pressure for the room, although in some
applications the offset airflow polarity can be flipped to instead
create a net positive pressure in the space vs. the corridor and or
other spaces. An exemplary application of the room offset airflow
command 32 being a two state control signal is for signal 32 to be
a value such as 10% of the maximum supply volume for normal room
operation. However, when a spill or other emergency condition is
detected such as a fire or smoke release via some sensor, alarm
system, or manually with an emergency exhaust switch 81, the room
offset airflow can be increased from its normal value by the
sampling system, building control system, or the system of FIG. 6.
Increasing the offset airflow to a potentially much higher value
will reduce the supply airflow volume so as to create a large
negative offset airflow for the room to provide a measure of
increased containment to prevent the spread of the spill vapors or
smoke into other spaces.
[0107] Finally FIG. 5 shows an embodiment of how command 47 for the
room exhaust airflow control device is created by first starting
with the supply flow feedback signal 58. The sum of the special
exhaust feedback signals 78 and 88 is subtracted from the supply
flow feedback signal 58 and added to the room offset airflow
command 32. The resultant signal is the room exhaust command signal
47 that is used to set and control the flow of the room exhaust
airflow control device 41.
[0108] FIG. 6 shows yet another facility monitoring system
embodiment of the invention that uses only individual space or duct
sensors located in the spaces or ducts to be monitored with no
centralized sensing of the embodiments of FIG. 1 or 2. This
embodiment can also combine and use the outputs of a plurality of
room sensors such as 425A and 427A or others located in room 20A or
in the room exhaust duct 40B of room 20B for dynamically varying
the dilution ventilation of a one-pass critical environment 20 such
as a laboratory or a vivarium. These one or more sensor outputs
from the same space or sensor outputs from multiple locations can
be combined as mentioned previously or used in a differential
manner.
[0109] Describing the embodiment of FIG. 6 in more detail, room 20A
contains two local or room sensors 425A and 427A. These sensors are
connected via cables 426A and 428A respectively to I/O block 430A
of the data acquisition and controller block 400A. These cables
could be of many different media depending on the output of the
sensor. For example, if these or other sensors have current or
voltage outputs, analog signal wires could be used for the cables.
If the output of the sensors 425A and 427A, or any other sensor, is
a digital signal, then typically a twisted pair or shielded twisted
pair would be used. If the output was of a digital optical or light
signal then a fiber optic cable could be used for these and other
local room sensors in FIG. 6.
[0110] Room sensors 425A and 427A could be one of many different
sensors. For example, they could be a particle counter and a TVOC
sensor or else they could be two or more of any of many other types
of sensors as mentioned previously such as CO, CO.sup.2, ozone,
radon, other toxic gases, ammonia, humidity, dew point temperature,
light, differential pressure, etc.
[0111] Additionally, room 20B in FIG. 6 shows the use of local duct
sensors such as individual sensors 443B and 445B mounted in the
room exhaust duct 40B as well as local duct sensors 543B and 545B
mounted in supply duct 50B. These four sensors are shown connected
into I/O block 430B of data acquisition and controller block 400B
through cables 444B, 446B, 454B, and 456B respectively. Similarly,
room 20C shows the use of room sensors 425C and 427C that are
connected to I/O block 430C of data acquisition and controller
block 400C through cables 426C, and 428C. I/O block 430C also is
monitoring duct sensors 463 and 465 that are mounted in an outside
air duct to measure outdoor air conditions. These sensors 463 and
465 are connected to I/O block 430C through cables 464 and 466
respectively. Any of the sensors shown in FIG. 6 could be used to
sense any one or more of the many air contaminants mentioned above
or any other type of air contaminant, air characteristic, or
building parameter of interest that can be sensed. Additionally,
although not shown in FIG. 6, any of the room switches or room
sensors shown in FIG. 1 or 2 such as occupancy switch 28C,
emergency exhaust switch 81, occupancy sensor 27B, etc. can also be
used with the embodiment of FIG. 6 by connecting these switches or
sensors into one or more of the inputs of the I/O blocks 430.
[0112] In FIG. 6 the data acquisition and controller blocks 400A,
400B and 400C also contain control logic blocks 410A, 410B and 410C
respectively. These control logic blocks are used to control the
functioning and logic of the data acquisition and controller blocks
400 as well as help communicate and interface through
communications cable media 401 with the other data acquisition and
controller blocks and or with another building system such as the
building control system 180. The data communications media 401 as
well as 201, 181, and 171 can be defined in the context of this
invention as a data network or communications cable which is part
of some form of digital data communications network implemented for
example with Ethernet or RS385 cable that runs a communications
protocol such as BACnet, Lonworks, or a building controls or other
building communications protocol such as Johnson Controls' Metasys
N1 or N2 bus. Alternatively, an IP or Internet Protocol could be
used.
[0113] The I/O block 430A like block 320A in FIG. 2 plus signal
processing block 420A are also used to create analog or digital
airflow control signals 31A and 32A for room 20A. In room 20B, the
signal processing controller block 420B also generates a dilution
ventilation airflow control signal 31B as an input into critical
environment airflow controller 30B, however in this example, the
controller 30B is a networked control device and receives all of
its control and feedback signals via communications network 401.
For this embodiment the airflow control signal 31B is in the form
of a software variable or other form of digital information that is
addressed to and received by the critical environments controller
30B. This type of networked control command 31B could likewise be
employed in the embodiments of FIG. 1 or 2 using for example the
digital communications media 201 of FIG. 2 or the building controls
communications media 181 of either FIG. 1 or 2.
[0114] In a similar manner any of the airflow control devices, air
contaminant sensors, or controllers described in FIGS. 1, 2, and 6
could be networked digital devices whereby the control, feedback,
and sensor signals could be digital information communicated
between the devices via a networked communications systems such as
a private LAN or local area network such as Ethernet or Arcnet, or
even via a public communications network such as the Internet.
[0115] FIG. 6 also indicates how a critical environment airflow
controller such as 30C can receive its control signals 31C and or
32C through the building control system 180 that is in
communication with the data acquisition and controllers 400.
Alternatively, all the data acquisition and controller functions
indicated in FIG. 6 may be implemented and performed by building
control system 180 without need for a separate data acquisition and
control system such as indicated by separate blocks 400. In this
latter case the controllers indicated by 400 would be implemented
by building control system controllers or through other control or
networked devices with control inputs and outputs of the type
commonly manufactured and used by building control companies such
as for example Johnson Controls with their Metasys system,
Honeywell with their Alerton subsidiary's native BACnet system
BACtalk, or Siemens with their Apogee system.
[0116] The signal processing controller blocks 420 or similar
blocks implemented with the building control system 180 are used to
combine the outputs of multiple air contaminant sensors using the
same approaches mentioned earlier for the embodiments of FIGS. 1
and 2. Similarly the dilution ventilation control signal 31 and the
offset airflow control signals 32 can be created using the same
methods mentioned earlier and can be of an output type such as two
or three state or VAV as mentioned before for the systems of FIGS.
1 and 2. Additionally any of the control or sensing approaches, or
control inputs or outputs mentioned in FIG. 1, 2 or 6 can be
applied to the systems or approaches of the other figures.
Similarly these same approaches or systems can be applied to a
facility monitoring system embodiment similar to that of either
FIG. 1 or 2 that is implemented not with a multipoint air sampling
system but instead using a fiber optic light packet sampling and
sensing system such as described in U.S. Pat. No. 6,252,689 and
referred to in this patent as a networked photonic sampling
system.
[0117] Using the systems of FIG. 1, 2, or 6, or the networked
photonic sampling system, there are several beneficial control
implementations and methods that can be implemented to solve
problems that occur when trying to vary the dilution ventilation in
a one-pass critical environment. For example, the outdoor air that
is being brought into the building may become slightly or
significantly contaminated by one or more air contaminants. Such
contaminants could include carbon monoxide from auto or truck
exhaust or from re-entrainment of furnace or boiler exhaust, high
levels of outdoor particulates, TVOC's that could be re-entrained
from fume hood or other special exhaust stacks, or other outdoor
sources of contaminants. If these contaminants are not filtered out
and pass into the supply air that is being fed into the labs it
could trigger the dilution ventilation controls to increase both
the room exhaust and supply air flows. Similarly, the increase in
supply air contaminants may not be high enough to trigger increased
supply air flow commands by itself, but added to existing
contaminant levels in the room it may make the system overly
sensitive to low or moderate contaminant levels originating from
within the room itself. Both of these problems can produce
potentially runaway results since the control action of increasing
supply air which contains air contaminants only serves to increase
the level of contaminant within the room. This can drive the supply
airflow levels even higher until no matter whether a two state,
three state, or VAV approach is used the supply airflow into the
room will eventually be commanded to its maximum level if the
outdoor air or supply system contamination is high enough. Since
the supply system airflow potentially feeds many rooms, potentially
all of these rooms could be pushed to their maximum flows. This
could result in the airflow capacity of the supply and or room
exhaust system being exceeded with resultant reductions of flow
into and out of the critical environment spaces and potential loss
of pressurization levels of these spaces vs. the corridor or other
rooms. If the special exhaust devices are also exhausted by the
room exhaust fans, then these devices may lose capture and
containment of hazardous fumes or vapors.
[0118] One exemplary control approach to solve this problem is to
use a differential measurement technique. In this approach an
outside air or supply air measurement is subtracted from room air
measurements to create differential measurements of the various air
contaminants of interest vs. either outside air or the supply air.
Thus, if the outside or supply air has an increase in particles,
CO, TVOC's, etc., the quality of the room air will be evaluated
against sources of contaminants in the room only since the effect
of the supply air sources will be subtracted out. Effectively, we
are concerned here not with the absolute quality of the room air
but whether it is being made worse by sources in the room or space
only, since increasing the dilution air will not make the room
cleaner if the dilution air is the source of the contaminant.
[0119] For example, as mentioned previously, we first start with
air contaminant measurements of the air in space 20A using for
example room sampling location 23A, room exhaust air duct sampling
location 43A, and or room sensor 25A in FIGS. 1 and 2, or room
sensors 425A, 427A, and or room exhaust duct sensor 443A of FIG. 6.
In this exemplary approach a measurement of the air contaminants is
next made of either the outside air using air sampling location 63
in FIG. 1 or 2 or air contaminant sensors 463 and 465 of FIG. 6 in
outside air intake duct 60 or the supply air using air sampling
location 53B in FIG. 1 or 2 or supply airflow duct sensors 543B and
545B in supply airflow duct 50B. If the spaces are receiving 100%
outside air directly from outdoors with no return air then a
measurement of outside air from within the outside air duct 60
going into the supply air handler will provide accurate results for
at least gas or VOC measurements. For at least particle
measurements, however, the measurement must be taken after the air
filters and fan systems such as at a location downstream of them
such as the supply duct locations mentioned above. If return air
from other areas is mixed with the outside air to produce the
supply air, then the use of a downstream supply duct airflow
measurement is also necessary with a location at least after where
the outside air and return air become well mixed. The use of only
one supply or outside air duct measurement should be sufficient for
all the spaces fed from a single air handler or main supply duct
since all the supply air flowing into these spaces from the same
air system should have similar characteristics and
contaminants.
[0120] Next each pair of air contaminant measurements (space air
and outside or supply air) is turned into a set of differential
measurements by subtracting the outside or supply air contaminant
measurement from the space air contaminant measurement. An example
of an embodiment to perform this is the subtraction block 35 of
FIG. 5 where a supply or outside air measurement of for example
TVOC's would be applied to the minus (-) input of the subtraction
block and the room or room exhaust duct air contaminant measurement
of TVOC's would then be applied to the positive (+) input. The
output would then be the differential measurement of TVOC's for
that space. Other methods of subtracting these air contaminant
measurements for software variables in a computerized control
system for example or for other implementations would be known to
those well skilled in the art.
[0121] The individual differential air contaminant measurements
would then be treated in the same manner described previously for
the non-differential room air measurements and thus would be used,
for example, individually or combined and then compared or analyzed
by signal processing controller block 130, 210, 530 or 420 of FIG.
1, 2, 4 or 6 respectively to create signals 31 and 32 that would be
used to vary the supply and exhaust airflows of space 20.
[0122] The air sampling embodiments of FIGS. 1 and 2 are preferred
embodiments for this differential measurement control concept since
the measurement of the supply or outside air and the space air
measurement can be performed with the same sensor within a
reasonably short period of time such as 5 to 30 minutes. As a
result many sensor errors are eliminated since they cancel out when
subtracting the two measurements. Consequently, very accurate
differential measurements can be made even when the increase in
contaminants in the room although important is relatively small
compared to a potentially high source level of outside air
contaminants. As a result these high outdoor background levels do
not substantially decrease the resolution or accuracy of the
measurement of the effects of any contaminant sources within the
critical environment spaces.
[0123] Another control approach that can be used with the
implementation of FIG. 1, 2 or 6 relates to a situation where a
high level of supply or outside air contaminant may be present, yet
the differential room air signal mentioned previously indicates
that there are not substantive sources of contaminants in the
space. In this situation the absolute level of contaminants in the
space may be high enough to trigger an increased dilution level,
but the differential signal correctly indicates that increasing the
supply air is not appropriate. In this situation, since the source
of the contaminant is the supply air, it may be advantageous to
reduce the supply air until the outside or source air contains a
lower level of contaminants.
[0124] One embodiment of this control approach consists of making
one or more air contaminant measurements in the supply duct 50B or
outside air intake duct 60 as mentioned previously. These one or
more contaminant measurements can then be combined or used
individually and then compared or analyzed by signal processing
controller block 130, 210, 530 or 420 of FIG. 1, 2, 4 or 6
respectively to determine if these signals exceed appropriate
trigger levels such as those used for the critical environment
spaces 20. If these trigger levels or appropriate trigger
conditions are met, then blocks 130, 210 or 420 can be used to
reduce the supply flow by one of several approaches. For example,
in FIG. 3 the temperature control output 93 of the Temperature
control block 90 can be completely overridden and effectively
disabled by a command output from signal processing controller
blocks 130, 210 or 420 so that the supply flow will become
controlled by the higher of either just the makeup requirements of
the special exhaust devices or the flow commanded by the dilution
ventilation command 31 which would be reduced to a low level.
[0125] Another control approach that can be used with the
implementation of FIG. 1, 2 or 6 relates to a situation where a
high level of contaminants may be present around the room or space
of interest particularly from a space such as the corridor which is
positive to the room of interest and from which the room's offset
airflow is drawn. In this situation, it may be desirable to create
a differential signal for each contaminant of interest as was
mentioned previously for outside or supply air. In this case, for
example, the measured air contaminants from room 20 would be
subtracted from the respective air contaminant measurements taken
from corridor 10 or from an anteroom, or other space which provides
at least a portion of room 20's offset airflow 21. When this
differential signal shows a high level it indicates that the source
of contaminants detected is in the room 20 not in the corridor 10
or other anteroom. This is important since in the case of someone
cleaning the corridor with a cleaning agent that gives off VOC's,
these VOC's will be pulled into all the rooms 20A, 20B and 20C that
feed from the corridor 10. As such if the absolute level of
contaminants or even the differential level of contaminants vs.
outside air or the supply air is high in the rooms 20 due to the
VOC's from the corridor it would throw all these rooms into a high
level of ventilation. Although this may be acceptable, it may also
cause problems with airflow capacity due to potentially all the
rooms going to a high level of dilution ventilation. To prevent
this airflow shortage condition from occurring, the differential
level of these rooms can be checked vs the corridor or equivalently
the absolute level of the corridor can be checked. Assuming the
corridor is positive to the spaces of interest, if either the
corridor level is high in any of the air contaminants of concern,
or the level of the room is high whereas the differential level of
the room compared to the corridor if low, then the correct control
action may be to increase the level of ventilation in the corridor,
but not to increase the level of ventilation in the room or only to
partially increase this level to some intermediate level. Another
means of implementing this control strategy is to only increase the
room 20's dilution ventilation command when both the differential
signal of the room to the supply (or outside air) is high and the
differential signal of the room 20 to the corridor 10 (or other
offset airflow source area) is also high.
[0126] Other strategies that could be implemented when these
differential signals and corridor signals indicate the source of
contamination is from the corridor 10 are to change the airflow
direction to make the rooms positive vs. the corridor. For example
there could be a source of smoke, VOC's or other contaminants
either in the corridor or from another room that has in turn
breached its containment and then contaminated the corridor. In
these situations, the appropriate action could be to use the signal
processing controller block 130, 210, 530 or 420 of FIG. 1, 2, 4 or
6 to sense this condition as mentioned above and then use the room
offset airflow control signals 32 to change the room 20's offset
airflow 21 from into the rooms to out of the room. This would also
require changing the corresponding offset airflow of the corridor
from positive to negative so the combination of the rooms 20 and
the corridor 10 remains balanced. In some cases the rooms 20 may
already be positive to the corridor 10. In this case it may be
advantageous to increase the level of positive offset airflow 21 to
an even greater value to ensure better protection from the
contaminants in the corridor 10. If the contaminant level in one of
the rooms is higher than any other room, then that room may likely
be the source of the contaminant. If that is the case then the
signal processing controller block 130, 210, 530, or 420 of FIG. 1,
2, 4, or 6 can be used to modify the offset airflow control signal
32 for that room 20 to make the room offset airflow 21 negative and
to as high a level as is appropriate, while also modifying the
corridor 10 offset airflow to the appropriate level. This concept
of balancing offset airflows in a corridor 10 vs. the rooms 20 off
from that corridor due to the need to change the offset airflows in
a room 20 is described in U.S. Pat. No. 5,545,086 entitled "Air
Flow Control For Pressurized Room Facility".
[0127] Although specific features of the invention are shown in
some drawings and not others, this is for convenience only as some
feature may be combined with any or all of the other features in
accordance with the invention.
[0128] Other embodiments will occur to those skilled in the art and
are within the following claims:
* * * * *
References