Respiratory protective devices. Compressed air line breathing apparatus with demand valve. Apparatus with a half mask at positive pressure. Requirements, testing, marking|Breathing apparatus, Compressed air, Supplied air breathing apparatus, Respirators, Valves, Flow regulators, Protective clothing, Safety devices, Flexible pipes, Pipe connections, Definitions, Ergonomics, Hygiene, Storage, Flammability, Pressure testing, Warning devices, Bend testing, Strength of materials, Flexibility, Thermal testing, Carbon dioxide, Electrostatics, Leak tests, Visual inspection (testing), Performance, Performance testing, Quality assurance, Test methods, Test equipment, Testing conditions, Mechanical testing, Laboratory testing, Marking, Instructions for use