What kind of respirator is classified as air-purifying?

An air-purifying respirator is designed to filter and clean the air of contaminants before it is inhaled by the user. Gas masks with canisters specifically fall into this category, as they use filters to remove particulate matter and specific gases from the air.

Self-contained breathing apparatus (SCBA) and supplied-air respirators provide breathable air from a source other than the ambient air, which does not fit the definition of air-purifying since they do not rely on filtering air. Instead, SCBAs carry their own air supply, while supplied-air respirators are connected to a stationary source of air. Therefore, among the choices presented, gas masks with canisters are the only type that purifies air through filtration and aligns with the classification of air-purifying respirators.