a method and system removes nuclear , biological and chemical agents from an air stream from a facility hvac . the system includes an irradiation zone , a saturation zone and a precipitation zone . a contaminant detection apparatus controls the irradiation , saturation and precipitation of the air stream . the irradiation destroys biological agents along with saturation of air stream with a water based solution . the biological debris and dissolved chemical agents are precipitated out of the air stream by condenser coils . nuclear agents are removed from the air stream by a diverting the air stream though a bypass filter containing high mass particulate filters and activated charcoal . the contaminants are stored for later removal and destruction . the contaminate detection apparatus includes nbc sensors .