Sufficient levels of oxygen must be present in the air to be filtered. Gas Masks Gas masks have full face coverage. The filtering cartridge or canister has a larger capacity than a cartridge type respirator. The cartridge may be mounted on the face piece or at the end of a flexible hose to allow mounting at the user's belt. Sufficient levels of oxygen must be present in the air where gas masks are used.
Gas masks provide protection against pesticides, and often toxic erbium materials.
The face pieces are similar to cartridge type respirators or gas masks. The air may be supplied by a portable air compressor or pressure tanks located up to 300 feet from the user. Compressors must be located in a clean air area. Supplied-air respirators can be used in confined spaces where there is likely to be an inadequate level of oxygen. Self-Contained Breathing Apparatus.