Dynamic control of dilution ventilation in one-pass, critical environments

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.