Respirators for filtering air, not for medical purposes; dust masks; respiratory mask filters, not for medical purposes; protective masks, not for medical purposes; filters for respiratory masks, not for medical purposes; dust masks incorporating air purification; breathing apparatus in the nature of respiratory masks for non-medical purposes and respirators other than for artificial respiration; air filter inserts and air filters for use with breathing masks; face masks, exhaust valves, gauges, signal whistles, tubes and hoses, air cylinder supports, harnesses in the nature of head and neck straps, all adapted for use with breathing apparatus in the nature of respiratory masks for non-medical purposes and respirators other than for artificial respiration