Make sure the cartridge brand matches the respirator brand. Gas Masks Gas masks, or chemical canister respirators, are very similar to chemical cartridge respirators except they can be used in areas where gases are extremely toxic or highly concentrated. The canisters hold more chemical sorbent than cartridges, so they have a greater filtering capacity and last longer. Canisters can be mounted on a belt, worn on the back or chest, or they can be screwed onto the mask beneath the chin. They're connected to the facepiece by an air hose.
Gas masks are only available with a full facepiece.
A PAPR is simply an air-purifying respirator with a motorized blower that forces air through the filtering device. It makes breathing easier for the wearer, so this type of respirator may be recommended by a doctor for someone with a minor respiratory or cardiovascular ailment. They tend to be cooler, too, because there is a constant stream of air over the wearer's face and head. Many PAPRs have a hard helmet and rigid visor under which the air is blown. PAPRs can be used for dusts, mists, gases, and vapors, provided you have the Air-powered Helmet right filters.