Gas mask cartridges are color coded to designate the type of contaminant that they filter. Before youchoose a filter, make sure you know what hazards you will be facing. Keep in mind that if there is a large concentration of a hazard in the air, the mask will not be able to completely protect you, even with theright cartridge. Here is the official chart from OSHA on cartridge color coding: ContaminantColor Coding on Cartridge/Canister acid gasesWhite hydrocyanic acid gasWhite with 1/2-inch green stripe completely around the canister near the bottom chlorine gasWhite with 1/2-inch yellow stripe completely around the canister near the bottom Organic VaporsBlack Ammonia gasGreen acid gases and ammonia gasGreen with 1/2-inch white stripe completely around the canister near the bottom Acid gases and ammonia gasGreen with 1/2-inch white stripe completely around the canister near the bottom Carbon monoxideBlue Acid gases and organic vaporsYellow Hydrocyanic acid gas and chloropicrin vaporYellow with 1/2-inch blue stripe completely around the canister near the bottom Acid gases, organic vapors, and ammonia gasesBrown Radioactive materials, except tritium & noble gases Purple (magenta) PesticidesOrganic vapor canister plus a particulate filter Multi-containment and CBRN agentOlive Any particulates - P100Purple Any particulates - P95, P99, R95, R99, R100Orange Any particulates free of oil - N95, N99, or N100Teal