Abstract:
A decontamination system for decontaminating an enclosure defining a chamber or region. The decontamination system includes an air bypass for introducing atmospheric air into the decontamination system and bypassing air to the atmosphere in response to system operating conditions. The air bypass allows increased airflow through the decontamination system during certain operating modes of the decontamination system (i.e., dehumidification and aeration phases), thereby reducing the amount of time needed to dehumidify and aerate the enclosure. The air bypass also facilitates the use of a high capacity dryer in the decontamination system.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of decontamination systems that use a decontaminant in its gaseous or vaporous phase, and more particularly to a decontamination system having an air bypass. 
     BACKGROUND OF THE INVENTION 
     Decontamination methods are used in a broad range of applications, and have used an equally broad range of decontaminating agents. As used herein the term “decontamination” refers to the inactivation of bio-contamination, and includes, but is not limited to, sterilization and disinfection. 
     Gaseous and vaporous decontamination systems rely on maintaining certain process parameters in order to achieve a target decontamination assurance level. For hydrogen peroxide vapor decontamination systems, those process parameters include the concentration of the hydrogen peroxide vapor, the degree of saturation, the temperature and pressure, and the exposure time. By controlling these process parameters, the desired decontamination assurance levels can be successfully obtained while avoiding condensation of the hydrogen peroxide due to vapor saturation. 
     Conventional vaporized hydrogen peroxide (VHP) decontamination systems for decontaminating enclosures (such as rooms or isolators), are generally closed-loop systems that contain a destroyer and a dryer within the system. In such closed-loop systems, a decontaminant is continuously conveyed through the enclosure. Decontaminant exiting the enclosure is directed to the destroyer to break down the vaporized hydrogen peroxide into water and oxygen. This type of arrangement allows the vaporized hydrogen peroxide concentration within the system to be maintained at a desired concentration depending on the airflow and decontaminant (typically 35% hydrogen peroxide, 65% water, by weight in a liquid state). 
     A conventional VHP decontamination system for decontaminating an enclosure has a decontamination cycle comprised of four (4) basic operating phases, namely, (1) a dehumidification phase, (2) a conditioning phase, (3) a decontamination phase, and (4) an aeration phase. In the dehumidification phase the relative humidity within the enclosure is reduced by using a dryer. After the dehumidification phase is complete, the conditioning phase commences, wherein vaporized hydrogen peroxide is injected into the enclosure at a relatively high rate to bring the hydrogen peroxide concentration up to a desired level in a short period of time. After the conditioning phase, the decontamination phase is run where the injection rate may be modified to maintain the hydrogen peroxide vapor in the enclosure at a constant concentration level. In the aeration phase that follows the decontamination phase, the enclosure is aerated by stopping injection of the hydrogen peroxide vapor, and removing hydrogen peroxide vapor from the enclosure. A destroyer may be used to break down the hydrogen peroxide vapor into water and oxygen. Aeration continues until the concentration of hydrogen peroxide in the enclosure is below a threshold concentration level (e.g., 1 ppm). 
     Existing closed-loop VHP decontamination systems have a system airflow that is limited by the capacity of the dryer used therein. In this respect, if the airflow exceeds the dryer capacity, the air circulated therethrough is inadequately dehumidified. Where the VHP decontamination system is being used with a large enclosure, the limited dryer capacity can be particularly disadvantageous. 
     Some dryers have their own internal blowers that are continuously operated at full speed in order to quickly dehumidify a maximum volume of air. However, where the dryer having its own internal blower is a high capacity dryer, the airflow provided by the internal blowers may exceed the airflow rate suitable for certain operating phases of a VHP decontamination system (e.g., decontamination phase). 
     The present invention overcomes the foregoing problems, along with others, by providing a VHP decontamination system including an air bypass that allows efficient utilization of a high capacity dryer having a continuously operating internal blower. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a decontamination system for decontaminating an enclosure defining a region, the decontamination system comprising: a dryer; a dryer conduit, said dryer disposed in said dryer conduit, wherein said dryer conduit has an input side upstream of said dryer and an output side downstream of said dryer; a supply conduit in fluid communication with the output side of said dryer conduit and said region defined by the enclosure; a vaporizer disposed in said supply conduit for vaporizing a liquid decontaminant to produce vaporized decontaminant; a secondary supply conduit in fluidly connectable with the output side of said dryer conduit and said supply conduit; a return conduit in fluid communication with said region and the input side of said dryer conduit; a first valve means moveable between a first position and a second position, wherein said input side of said dryer conduit is in fluid communication with atmospheric air when the first valve means is in the first position; a second valve means moveable between a first position and a second position, wherein said output side of said dryer conduit is in fluid communication with atmosphere when said second valve means is in the first position, and said output side of said dryer conduit is in fluid communication with said secondary supply conduit when said second valve means is in the second position; and control means for controlling operation of said first and second valve means. 
     In accordance with another aspect of the present invention, there is provided a method for decontaminating a region defined by an enclosure using a vaporized decontaminant, the method comprising: circulating fluid from the region through a flow path to remove moisture therefrom, said flow path including a dryer conduit having a dryer disposed therein, said dryer conduit having an input side upstream of said dryer and an output side downstream of said dryer; putting the input side of the dryer conduit in fluid communication with atmospheric air and the output side of the dryer conduit in fluid communication with atmosphere, when the humidity within the region reaches a predetermined humidity level. 
     In accordance with still another aspect of the present invention, there is provided A decontamination system for decontaminating an enclosure defining a region, the decontamination system comprising: a circulation system in fluid communication with the region, said circulation system defining a closed loop fluid flow path to circulate fluid through the region; a bypass system in fluid communication with atmospheric air and the circulation system, said bypass system defining a bypass fluid flow path; and means for controlling the flow of atmospheric air through the bypass fluid flow path. 
     An advantage of the present invention is the provision of a VHP decontamination system that is adapted for efficient use of a high capacity air dryer. 
     Another advantage of the present invention is the provision of a VHP decontamination system that allows increased airflow through the system. 
     Still another advantage of the present invention is the provision of a VHP decontamination system that allows an increased dehumidification rate. 
     Still another advantage of the present invention is the provision of a VHP decontamination system that allows an increased aeration rate. 
     Yet another advantage of the present invention is the provision of a VHP decontamination system that regulates the use of available airflow capacity. 
     These and other advantages will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawing which form a part hereof, and wherein the FIGURE is a schematic view of a vaporized hydrogen peroxide (VHP) decontamination system illustrating a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for the purposes of illustrating a preferred embodiment of the invention only and not for the purposes of limiting same, the FIGURE shows a vaporized hydrogen peroxide (VHP) decontamination system  10 , illustrating a preferred embodiment of the present invention. System  10  is used with an enclosure  12  that defines an inner decontamination chamber or region  14 . By way of example, and not limitation, enclosure  12  may take the form of an isolator, room or other sealed enclosure. The present invention is preferably used with regions or chambers having a volume of 300 cubic feet or smaller. However, it is contemplated that the present invention may also be used with larger regions or chambers. Articles to be decontaminated may be disposed within enclosure  12 . Enclosure  12  includes an inlet port  20  and an outlet port  40 . 
     System  10  includes a “closed loop” circulation system that is comprised of a plurality of conduits connected between inlet port  20  and outlet port  40  of enclosure  12 . In the illustrated embodiment, the circulation system includes a supply conduit  22 , a secondary supply conduit  24 , a dryer conduit  32 , and a return conduit  42 . Supply conduit  22  is in fluid communication with dryer conduit  32  and region  14  via inlet port  20 . Return conduit  42  is in fluid communication with dryer conduit  32  and region  14  via outlet port  40 . A first end of dryer conduit  32  is in fluid communication with return conduit  42 , as indicated above, while a second end of dryer conduit  32  terminates at a first port of a three-way bypass outlet valve  82 . A second port of three-way bypass outlet valve  82  is connected with a first end of secondary supply conduit  24 , and a third port of three-way bypass outlet valve  82  is connected with a first end of a bypass outlet conduit  38 . A second end of secondary supply conduit  24  is in fluid communication with supply conduit  22 . A second end of bypass outlet conduit  38  is in fluid communication with atmospheric air. The circulation system defines a primary fluid flow path “A” (indicated by the solid arrows) and secondary fluid flow path “B” (indicated by the short dashed arrows), as will be described in further detail below. 
     In the illustrated embodiment, bypass outlet valve  82  has only two positions. In a first position, bypass outlet valve  82  puts second end of dryer conduit  32  in fluid communication with secondary supply conduit  24 . In a second position, bypass outlet valve  82  puts second end of dryer conduit in fluid communication with bypass outlet conduit  38 . 
     A bypass inlet conduit  36  has a first end in fluid communication with dryer conduit  32  and return conduit  42 , and a second end in fluid communication with atmospheric air. A bypass inlet valve  72  is disposed in bypass inlet conduit  36  to control the flow of atmospheric air through bypass inlet conduit  36 . 
     System  10  includes a bypass system that is comprised of a plurality of conduits that are in fluid communication with the atmosphere and the circulation system described above. In the illustrated embodiment, bypass system includes bypass inlet conduit  36 , dryer conduit  32  and bypass outlet conduit  38 . The bypass system defines a bypass fluid flow path “C” (indicated by the long dashed arrows), as will be described in further detail below. 
     A vaporizer  130  is disposed in supply conduit  22 . Vaporizer  130  includes a vaporization chamber (not shown), wherein a liquid decontaminant is heated to form a gaseous or vaporized decontaminant. A feed conduit  52  connects a liquid decontaminant supply  160  with vaporizer  130 . Decontaminant supply  160  may include a replaceable cartridge. A conventionally known balance device (not shown) may also be associated with decontaminant supply  160 , to measure the actual mass of liquid decontaminant being supplied to vaporizer  130 . A typical decontaminant is an aqueous solution of hydrogen peroxide comprised of about 35% by weight hydrogen peroxide and about 65% by weight water. 
     In accordance with the illustrated embodiment, vaporizer  130  includes an internal heater (not shown), a thermal cutoff or over-temperature switch (not shown), and a temperature sensor  144 . The internal heater of vaporizer  130  heats the liquid decontaminant supplied by decontaminant supply  160 , thereby vaporizing the decontaminant by conventionally known means. In the illustrated embodiment, the liquid decontaminant is an aqueous solution of hydrogen peroxide. The vaporized hydrogen peroxide produced by vaporizer  130  is supplied to region  14  of enclosure  12  via supply conduit  22 . The thermal cutoff or over-temperature switch of vaporizer  130  automatically cuts power to the vaporizer heater in the event that a predetermined temperature limit has been exceeded. Temperature sensor  144  provides a signal indicative of the temperature of the fluid inside the vaporization chamber of vaporizer  130 . 
     An injection pump  170  driven by a motor  172  is provided to convey metered amounts of the liquid decontaminant to vaporizer  130 . In an alternative embodiment, pump  170  is provided with an encoder (not shown) that allows monitoring of the amount of decontaminant being metered to vaporizer  130 . If an encoder is provided with pump  170 , a balance device for decontaminant supply  160  is not required. 
     A filter  176  is provided in feed conduit  52  to filter the liquid decontaminant before it is received by vaporizer  130 . A pressure switch  174  is also provided in feed conduit  52 . Pressure switch  174  is operable to provide an electrical signal in the event that a certain static head pressure does not exist in feed conduit  52 . 
     An injection blower  110  and an air preheater  120  are located within supply conduit  22 , upstream from vaporizer  130 . Injection blower  110 , driven by a motor  112 , is disposed within supply conduit  22  between vaporizer  130  and dryer conduit  32 . Blower  110  is operable to circulate fluid through supply conduit  22 . Air preheater  120  is disposed within supply conduit  22  between blower  110  and vaporizer  130 . Air preheater  120  heats the fluid passing therethrough. A thermal cutoff or over-temperature switch (not shown) automatically cuts power to heater  120  in the event that a predetermined temperature limit has been exceeded. A temperature sensor  124  provides a signal indicative of the temperature of the fluid inside air preheater  120 . 
     A flow sensor  150  and a high efficiency particulate air (HEPA) filter  152  are located within supply conduit  22 , downstream from vaporizer  130 . Flow sensor  150  is disposed in supply conduit  22  between vaporizer  130  and enclosure  12 . Flow sensor  150  provides a signal indicative of the fluid flow rate through supply conduit  22 . A temperature sensor  148  is located in supply conduit  22  proximate to flow sensor  150  to provide a signal indicative of the temperature of the fluid flowing through supply conduit  22 . Filter  152  is disposed within supply conduit  22  between flow sensor  150  and enclosure  12 . Fluid is filtered by filter  152  before entering region  14  of enclosure  12 . 
     In the illustrated embodiment, a chemical agent conduit  54  connects a chemical agent supply  180  to supply conduit  22 , between flow sensor  150  and filter  152 . A valve  192  is disposed within chemical agent conduit  54  to control the flow of chemical agent (e.g., ammonia) from chemical agent supply  180  to supply conduit  22 . 
     Referring now to return conduit  42 , a circulation blower  66 , driven by a motor  68 , is disposed within return conduit  42  between enclosure  12  and dryer conduit  32 . Circulation blower  66  is operable to circulate fluid through return conduit  42 . A catalytic destroyer  60  is disposed in return conduit  42  between blower  66  and enclosure  12 . Catalytic destroyer  60  is operable to destroy hydrogen peroxide flowing therethrough, by converting hydrogen peroxide into water and oxygen, as is conventionally known. 
     In the illustrated embodiment, a HEPA filter  62  is preferably disposed between destroyer  60  and enclosure  12 , and a carbon filter  64  is disposed between blower  66  and destroyer  60 . Carbon filter  64  used to filter chemical agents from the fluid stream. 
     A dryer  90  is disposed within dryer conduit  32  to remove moisture from the fluid blown through dryer conduit  32 . Accordingly, dryer conduit  32  has an input side that is upstream of dryer  90  and an output side that is downstream of dryer  90 . Dryer  90  is preferably a conventionally known regenerative desiccant dryer that collects water vapor from the fluid stream passing therethrough. Regenerative desiccant dryers use a desiccant (e.g., silica gel, activated alumina and molecular sieve), which adsorbs water vapor in the fluid stream. It should be understood that dryer  90  may take other forms including a refrigerated dryer. In the illustrated embodiment, dryer  90  also includes a high-volume internal blower  100 , driven by a motor  102 . Dryer  90  may also be put in fluid connection with a regeneration unit (not shown) via a regeneration conduit  48 . The regeneration unit regenerates the desiccant by driving off moisture in a regeneration process that includes applying dry, expanded purge air, heat, or a combination of both. By way of example, and not limitation, dryer  90  may have a drying capacity (i.e., maximum volume of air through the dryer per unit time) in the range of 120 to 6000 cubic meters of air per hour. Motor  102  may have a horsepower in the range of 1 to 20 hp (i.e., dryer “size”). Examples of suitable desiccant and refrigerated dryers include, by are not limited to, dryer model nos. MG90, MG150 and HCD-4500, from Munters of the United Kingdom. 
     A concentration sensor  15 , a pressure sensor  16 , and a humidity sensor  18  are located inside region  14  of enclosure  12 . Concentration sensor  15  provides a signal indicative of the concentration of hydrogen peroxide in region  14 . Pressure sensor  16  provides a signal indicative of the pressure level within region  14 . Humidity sensor  18  provides a signal indicative of the humidity level within region  14 . 
     As discussed above, a “closed loop” circulation system defines a primary fluid flow path “A” and secondary fluid flow path “B.” Primary fluid flow path “A” is defined from vaporizer  130  through supply conduit  22  to region  14 , through return conduit  42  to destroyer  60  and dryer conduit  32 , through dryer conduit  32  to dryer  90 , and to air preheater  120  and vaporizer  130  through supply conduit  22 . Secondary fluid flow path “B” is defined from dryer conduit  32  (at outlet of dryer  90 ) through secondary supply conduit  24 . In this respect, vaporizer  130  and air preheater  120  along supply conduit  22  are bypassed in secondary fluid flow path “B.” 
     As noted above, the bypass system defines a bypass fluid flow path “C.” Bypass fluid flow path “C” is defined by bypass inlet conduit  36 , through dryer conduit  32  to dryer  90 , and continuing through dryer conduit  32  and bypass outlet conduit  38  to atmosphere. 
     A control system  200  controls operation of VHP decontamination system  10 . Control system  200  includes a controller  202  that preferably takes the form of a conventional microcontroller or microcomputer. Vaporizer  130 ; motors  68 ,  112 ,  172 ; heater  120  and the internal heater of vaporizer  130 ; and valves  72 ,  82 ,  192 , are controlled by control signals transmitted by controller  202 . Controller  202  receives data signals from flow sensor  150 ; temperature sensors  124 ,  144 ,  148 ; concentration sensor  15 ; pressure sensor  16 ; humidity sensor  18 ; and pressure switch  174 . 
     The present invention shall now be further described with reference to the operation of VHP decontamination system  10 . VHP decontamination system  10  has four (4) basic operating phases, namely, a dehumidification phase, a conditioning phase, a decontamination phase, and an aeration phase. In the dehumidification phase the relative humidity within region  14  of enclosure  12  is reduced by using dryer  90  to remove water vapor therefrom. After the dehumidification phase is completed, the conditioning phase commences, wherein liquid decontaminant (i.e., an aqueous solution of hydrogen peroxide) is vaporized by vaporizer  130  and injected into region  14  at a relatively high rate to rapidly increase the concentration of hydrogen peroxide inside region  14 . Following the conditioning phase, the decontamination phase commences wherein the decontaminant injection rate is regulated to maintain the hydrogen peroxide concentration inside region  14  at a desired constant concentration level In the aeration phase that follows the decontamination phase, enclosure  12  is aerated by stopping injection of the vaporized hydrogen peroxide into region  14 , and removing hydrogen peroxide therefrom. Aeration continues until the hydrogen peroxide concentration level in region  14  is below an allowable threshold concentration level (e.g., 1 ppm). 
     Initially, controller  202  transmits control signals to turn off motors  68 ,  110  and  172 . Accordingly, circulation blower  66 , injection blower  110  and injection pump  170  are inactive. Controller  202  transmits a first control signal to move bypass inlet valve  72  to a closed position (thereby preventing atmospheric air from entering system  10 ), and a second valve control signal to move bypass outlet valve  82  to a position wherein dryer conduit  32  is in fluid communication with secondary supply conduit  24 . It should be understood that in the illustrated embodiment of the present invention, motor  102  of internal blower  100  (associated with dryer  90 ) remains active throughout all four (4) of the operating phases of VHP decontamination system  10 , described in detail below. The continuous activation of motor  102  of internal blower  100 , prevents overheating of the desiccant of dryer  90 . 
     As indicated above, a typical decontamination cycle includes a dehumidification phase, a conditioning phase, a decontamination phase and an aeration phase. Each of these operating phases will now be described in detail. 
     Dehumidification Phase 
     When the dehumidification phase is first initiated, controller  202  transmits control signals to turn on heater  120  and the internal heater of vaporizer  130 , and to activate motors  68 ,  112 . Accordingly, circulation blower  66  and injection blower  110  are activated. As indicated above, bypass inlet valve  72  is in the closed position, and bypass outlet valve  82  is in a position wherein dryer conduit  32  is in fluid communication with secondary supply conduit  24 . Consequently, circulation blower  66  and injection blower  110  cause fluid circulation through “closed loop” fluid flow paths “A” and “B,” thereby rapidly dehumidifying region  14 . In this regard, air drawn out of region or enclosure  14  by circulation blower  66  is conveyed through dryer  90  to remove moisture therefrom. Dehumidified air exiting dryer  90  is drawn into supply conduit  22  by injection blower  110 . Prior to injection into region  14 , air preheater  120  and the internal heater of vaporizer  130  heat the dehumidified air stream as it travels through supply conduit  22 . Additional dehumidified air follows secondary flow path “B.” 
     As indicated above, humidity sensor  18  located inside region  14  provides a signal to controller  202  indicative of the humidity level inside region  14 . When controller  202  determines that the desired humidity level in region  14  has been reached, controller  202  transmits a control signal to open bypass inlet valve  72 , thereby allowing atmospheric air to be drawn into bypass inlet conduit  36 , and through dryer  90 . At this time, controller  202  also transmits a control signal to the bypass outlet valve  82  to move bypass outlet valve  82  to a position, wherein dryer conduit  32  is in fluid communication with the atmosphere via bypass outlet conduit  38 . As a result, fluid flow along flow path “B” ends and fluid flow along bypass flow path “C” commences. Accordingly, some fluid traveling through dryer conduit  32  will be directed to the atmosphere through bypass outlet conduit  38 . It should be understood that fluid flow continues along flow path “A” since injection blower  110  and circulation blower  66  remain active. 
     Conditioning Phase 
     The conditioning phase follows the dehumidification phase described above. Bypass inlet valve  72  remains open and bypass outlet valve  82  remains in a position wherein dryer conduit  32  is in fluid communication with the atmosphere via bypass outlet conduit  38 . Accordingly, fluid flow continues along bypass flow path “C.” Controller  202  transmits control signals to motor  68  (associated with circulation blower  66 ) to maintain a predetermined pressure level (positive or negative) within region  14 , as indicated by pressure sensor  16 . Controller  202  also transmits a control signal to motor  112  (associated with injection blower  110 ) to maintain a predetermined fluid flow through supply conduit  22 , based upon feedback data received by controller  202  from flow sensor  150 . Therefore, fluid flow also continues along flow path “A.” 
     Since bypass outlet valve  82  remains in a position wherein dryer conduit  32  is in fluid communication with the atmosphere via bypass outlet conduit  38 , injection blower  110  will draw only the amount of air from the outlet of dryer  90  that is required to maintain the predetermined fluid flow through supply conduit  22 . In this respect, excess air that is output from dryer  90  exits system  10  to the atmosphere via bypass outlet conduit  38 . Filters  62  and  64 , and destroyer  60  operate to ensure that no biological, chemical, or hydrogen peroxide exit to the atmosphere via bypass outlet conduit  38 . 
     Heater  120  and the internal heater of vaporizer  130  also remain turned on during the conditioning phase. Controller  202  activates injection pump  170  by transmitting control signals to motor  172 . Injection pump  170  supplies metered amounts of liquid hydrogen peroxide to vaporizer  130 . The liquid hydrogen peroxide is vaporized in vaporizer  130  in a conventionally known manner. The vaporized hydrogen peroxide is injected into region  14  via supply conduit  22  at a relatively high rate to rapidly increase the concentration of hydrogen peroxide inside region  14  to a desired level suitable for a decontamination operation. 
     Decontamination Phase 
     Once the hydrogen peroxide has reached the desired concentration level within region  14 , the decontamination phase may commence. In the decontamination phase, VHP decontamination system  10  continues to generally operate in the same manner described above for the conditioning phase. Thus, there is fluid flow along flow paths “A” and “C.” However, controller  202  modifies the speed of motor  172  associated with injection pump  170  in order to maintain a generally constant concentration of hydrogen peroxide in region  14  that is suitable for decontamination. 
     If an additional chemical agent (e.g., ammonia) is to be injected into region  14  during the decontamination phase, controller  202  transmits control signals to move valve  192  to an open position until the desired concentration of the chemical agent is reached in region  14  for a predetermined period of time. Controller  202  may cycle valve  192  between the open and closed positions, as necessary, to maintain the desired concentration of the chemical agent. 
     The decontamination phase is run for a predetermined period of time, preferably with the concentration level of the vaporized hydrogen peroxide in region  14  remaining at a generally constant level, for a predetermined period of time that is sufficient to effect the desired decontamination. 
     Aeration Phase 
     As indicated above, the aeration phase follows the decontamination phase. After the decontamination phase is completed, controller  202  transmits a control signal to turn off motor  172  associated with injection pump  170 , thereby shutting off the flow of liquid hydrogen peroxide to vaporizer  130 . Controller  202  also transmits a control signal to close bypass inlet valve  72  to prevent atmospheric air from being drawn into VHP decontamination system  10  via bypass inlet conduit  36 . In addition, controller  202  transmits a control signal to bypass outlet valve  82  to move bypass outlet valve  82  to a position wherein dryer conduit  32  is in fluid communication with secondary supply conduit  24 , thereby directing fluid flow from dryer  90  into region  14 . Accordingly, fluid flow along bypass flow path “C” ends, and fluid flow along flow path “B” commences. 
     In the aeration phase, controller  202  transmits control signals to motor  68  to operate circulation blower  66  at or near full speed. Injection blower  110  may also be active during the aeration phase. Thus, fluid circulates along flow paths “A” and “B” during the aeration phase. 
     Hydrogen peroxide vapor withdrawn from region  14  by blower  66  is broken down into water and oxygen by destroyer  60 . As a result, the concentration of hydrogen peroxide in region  14  of enclosure  12  is reduced below a threshold level (e.g., 1 ppm). 
     A decontamination cycle is complete following the aeration phase. A subsequent decontamination cycle commences with a dehumidification phase, as described above. 
     Other modifications and alterations will occur to others upon their reading and understanding of the specification. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.