Gas Mask Canister NIOSH Rating Ammonia (AM) Chlorine (CL) Chlorine Dioxide (CD) Chloroacetophenone (CN) Chlorobenzylidene Malononitrile (CS) Formaldehyde (FM) HEPA Hydrogen Chloride (HC) Hydrogen Fluoride (HF) Methylamine (MA) Organic Vapor (OV) Phosphine