Microbicidal air filter for use with an air passageway, which includes an immobilization network including fibers having substantially embodied therein an amount of at least one antimicrobial agent sufficient to substantially immobilize, retain and kill microbes suspended in a volume of air moving through the air passageway. The immobilization network is substantially permeable to air. A microbicidal facemask and a microbicidal air filter used in an air circulation system using the immobilization network are disclosed.