Air supply system particularly suited to remove contaminants created by chemical, biological or radiological conditions

Abstract

Disclosed is an air supply system that provides filtered ventilation to a protected zone which is maintained at a positive pressure so as to prevent contaminants from infiltrating therein. The system further discloses a three-stage air filter apparatus that provides all the necessary filtering to remove contaminants from the air that may be created by chemical, biological and radiological conditions.

1. A system for supplying an enclosed protected zone having air intake means with an air supply having an inlet and that is filtered to remove contaminates created by chemical, biological or radiological conditions, said system comprising:
 a) a three-stage air filter apparatus having an input fluidly coupled to said inlet and having an output, said three-stage air filter apparatus having first, second and third coaxially arranged annular filters, with the first filter being disposed within the second filter and the second filter being disposed within the third filter, and with the first filter being positioned closest to said input and the third filter being positioned closest to said output, said first filter filtering and removing particulates of at least a first size, said second filter filtering and removing aerosols and particulates of a size which is less than said first size, and said third filter comprising a gas adsorber for removing gases; and  
 b) a supply fan having an input fluidly coupled to said output of said three-stage air filter apparatus and an output fluidly coupled to said air intake means of said protected zone, said supply fan supplying an air at a sufficient enough flow so as to provide said protected zone with a positive pressure.  
 
   
   
     2. The system according to  claim 1  further comprising at least one differential transducer connected between the input and output of the said three-stage air filter apparatus and delivering an output proportional to the difference between the pressure sensed therebetween. 
   
   
     3. The system according to  claim 1 , wherein said positive pressure of said protected zone is within the range from about 0.5 in wg to about 1.5 in wg. 
   
   
     4. The system according to  claim 3  further comprising a transducer connected within said protected zone and delivering an output proportional to the pressure sensed within said protected zone. 
   
   
     5. The system according to  claim 4 , further comprising an alarm device connected to receive the output of said transducer and generating an alarm signal when said output of said transducer is representative of a pressure of below about 0.5 in. wg. 
   
   
     6. The system according to  claim 3 , wherein said protected zone has an opening with an input and an output and wherein said system further comprises a pressure control valve (PCV) fluidly coupled between the input and output of said opening of said protected zone and is dimensioned so as to allow for fluid communication between said input and output when the positive pressure within said protected zone is greater than about 1.5 in wg. 
   
   
     7. The system according to  claim 1  further comprising a coarse filter interposed between said inlet of said supply fan and said input of said three-stage air filter apparatus, said coarse filter filtering and removing particulates having a size which is greater than said first size. 
   
   
     8. The system according to  claim 7  further comprising a heater interposed between said coarse filter and said input to said three-stage air filter apparatus, said heater being selected so as to elevate the air flowing thereacross to a temperature of greater than about 42° F. and having a relative humidity of about 70%. 
   
   
     9. The system according to  claim 1  further comprising cooling coils interposed between said output of said three-stage air filter apparatus and said input of said supply fan; 
   
   
     10. The system according to  claim 1 , wherein said first and second and third filters of said three-stage air filter apparatus are selected to remove particulates, aerosols and gas created by chemical, biological or radiological conditions. 
   
   
     11. A method for supplying an enclosed protected zone having air intake means with an air supply having an inlet that is filtered to remove contaminates created by chemical, biological or radiological conditions, said method comprising the steps of:
 a) providing a three-stage air filter apparatus having an input fluidly coupled to said inlet and an outlet, said three-stage air filter apparatus having first, second and third coaxially arranged annular filters, with the first filter being disposed within the second filter and the second filter being disposed within the third filter, and with the first filter being positioned closest to said input and the third filter being positioned closest to said output, said first filter filtering and removing particulates of ar least a first size, said second filter filtering and removing aerosols and particulates of a size which is less than said first size, and said third filter comprising a gas adsorber for removing gases; and  
 b) providing a supply fan having an input fluidly coupled to said output of said three-stage air filter apparatus and an output fluidly coupled to said air intake means of said protected zone, said supply fan supplying a sufficient flow of air so as to provide said protected zone with a positive pressure within the range from about 0.5 in wg. to about 1.5 in wg.  
 
   
   
     12. The method according to  claim 11  further comprising step of arranging at least one differential transducer between the input and output of the three-stage air filter apparatus and delivering an output proportional to the difference between the pressure sensed therebetween. 
   
   
     13. The method according to  claim 11 , further comprising the step of arranging a transducer within said protected zone and delivering an output proportional to the pressure sensed therein. 
   
   
     14. The method according to  claim 13 , further comprising the step of providing an alarm device connected to receive the output of said transducer and generating an alarm signal when said output of said transducer is representative of a pressure of below about 0.5 in wg. 
   
   
     15. The method according to  claim 11 , wherein said protected zone has an opening with an input and an output and wherein said method further comprises the step of:
 a) providing a pressure control valve (PCV) fluidly coupled between the input and output of said opening of said protected zone; and  
 c) dimensioning said PCV to allow for fluid communication between said input and output when the positive pressure within said protected zone is greater than about 1.5 wg.  
 
   
   
     16. The method according to  claim 11  further comprising the step of:
 a) providing a coarse filter interposed between said inlet of said supply fan and said input of said three-stage air filter apparatus, said coarse filter filtering and removing particulates having a size which is greater than said first size.  
 
   
   
     17. The system according to  claim 16  further comprising the step of:
 a) providing a heater interposed between said coarse filter and said input to said three-stage air filter apparatus; and:  
 b) dimensioning said heater to elevate the air flowing thereaccross to a temperature of greater than about 42° F. and having a relative humidity of about 70%.  
 
   
   
     18. A system for supplying an enclosed protected zone with air cleaned of chemical, biological, and radiological contaminants at a flow rate sufficient to maintain a positive pressure within the protected zone, comprising:
 a free-standing first filter that filters and removes particulates of at least a first size from the air;  
 a free-standing second filter that filters and removes aerosols and particulates of a size which is less than the first size from the air;  
 a free-standing third filter that adsorbs gases from the air; and  
 a blower pneumatically coupling the downstream side of the third filter with the protected zone,  
 wherein: 
 the first, second and third filters are annular filters axially nested one inside the other in the recited order; and  
 the first, second, and third filters are radial flow filters.  
 
 
   
   
     19. The system according to  claim 18 , further comprising:
 a filter housing including an axial opening for receiving the first, second, and third filters, and an annular opening receiving cleaned air from the downstream side of the third filter, and  
 a plenum pneumatically coupling the annular opening and the blower.