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 . 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 . 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 . 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 . 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 .
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 , 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 .