Both disposable and reusable masks are available. Usually a single respirator offers protection only against dusts and mists but a few will protect against dusts, mists and fumes. Filters and disposable masks should be replaced when breathing becomes too labored, when the mask loses its shape and no longer seals well to your face, or if you taste or smell the substance. Nuisance dust masks are most easily distinguished by their single elastic strap. They will not, however, provide adequate protection from pesticide dusts and mists.
Approved models have two elastic straps in back for a better seal.
Chemical Cartridge Respirators Chemical cartridge respirators filter out low concentrations of toxic gases and vapors. An absorbent material such as activated charcoal absorbs contaminants from inhaled air. These masks can also be equipped with particulate filters, so if you'll be exposed to gases or vapors and dusts or mists, this is the kind of respirator you should wear. The half Chemical Cartridge Respirator masks are a so available in disposable or reusable models. The filtering cartridges for these respirators screw onto the front of the mask.