Canister is effective against dusts, fumes, and mists having a TWA less than 0.05 mg/m3 and radio nuclides, but it is not for use in atmospheres containing less than 19.5% oxygen nor for entry into atmospheres that are immediately dangerous to life and health. In the case of serious biological threats such as anthrax, the mask will only give some protections to the user, but a full-protective suit is the only way to guarantee protection from significant exposure. User should not expect to be able to stay in an affected area for any period of time. The gas mask simply buys more time to get out.