Respiratory protective devices. Self-contained closed-circuit breathing apparatus compressed oxygen or compressed oxygen-nitrogen type. Requirements, testing, marking|Grades (quality), Performance testing, Carbon dioxide, Test equipment, Design, Pressure, Breathing apparatus, Fire tests, Nitrogen, Relief valves, Gas-resistance tests, Hose connectors, Respirators, Heating tests, Life (durability), Resistance measurement, Performance, Moisture, Tensile strength, Instructions for use, Supplied air breathing apparatus, Designations, Pressure testing, Mechanical testing, Pressure gauges, Mass, Compressed gases, Leak tests, Pressure regulators, Electrical insulation, Environment (working), Low-temperature testing, Testing conditions, Thermal testing, Marking, Storage, Breathing bags, Determination of content, Valves, Oxygen, Warning devices, Flexible pipes