Respiratory protective devices for use against chemical, biological, radiological and nuclear (CBRN) agents. Powered air purifying respirators. Specification|Leak tests, Supplied air breathing apparatus, Firefighting, Biological hazards, Chemical-resistance tests, Classification systems, Gas-resistance tests, Chemical hazards, Respirators, Decontamination, Designations, Radiation hazards, Emergency equipment, Marking, Emergency services, Safety devices, Breathing apparatus, Performance, Nuclear radiation