Heading 9020 requires that the gas mask or breathing appliance have mechanical parts (such as valves or a harness assembly) and/or replaceable filter cartridges. A simple disposable filtering facepiece without these features — such as a basic N95-style mask — does not meet this criterion and classifies under a different heading. The presence of a replaceable filter system or a demand-valve mechanism is the practical dividing line.

NIOSH certification is required for self-contained breathing apparatus and air-purifying respirators intended for occupational use in the United States under OSHA-regulated environments. While CBP does not enforce NIOSH certification at the border as an admissibility condition, selling non-certified respirators for occupational use can violate OSHA and FTC regulations. Importers should confirm certification status before distribution.