Classification of dust masks and gas masks that protect workers' respiratory systems from dust and hazardous substances in manufacturing sites. Includes disposable and replaceable filter-type masks that protect respiratory systems from metal powder, abrasive dust, welding fumes, and organic solvent vapors generated during cutting, grinding, welding, and painting operations. Focuses on nationally certified products (DS1, DS2, RS1, RS2 standards) and combination products with gas mask absorption canisters, classified as dedicated respiratory protection equipment distinct from helmets and safety glasses.