Chemical Cartridge/Gas Mask respirator. Gas masks are also known as “air-purifying respirators” because they filter or clean chemical gases and possibly particles out of the air as you breathe. This respirator includes a facepiece or mask, and a filter/cartridge (if the filter is in a metal shell it is called a “canister”). Straps secure the facepiece to the head. The cartridge may have a filter to remove particles (such as a biological weapon), charcoal (to remove certain chemicals), both, or other parts. When the user inhales, air is pulled through the filter.