an antimicrobial air filter has a layer of fabric bearing porous activated carbon particulate deodorizing agents , a layer of polymeric expanded foam filter media impregnated with a biostat type antimicrobial agent and a pleated sheet of hepa filtration media treated with the biostat . the layers are assembled such that the biostat does not migrate into the porous carbon particulates . the filter may be used in central air conditioning and heating systems without the need for an air circulator in addition to those conventionally employed .