Compressed Breathing Air
Compressed breathing air is subject to strict limits of harmful contaminants defined in European standard EN 12021 and various defense standards such as DEF STAN 68-284 issue 3. The testing interval of breathing air compressors and associated equipment is 3 months and gases tested include carbon monoxide, carbon dioxide and oil vapor defined as hexane and heavier hydrocarbons. EN 12021 covers underwater applications including self-contained open-circuit compressed gas breathing (SCUBA) and compressed gas line breathing (hard-helmet diving), respiratory equipment used on the ground for escaping from toxic atmospheres and for working in contaminated atmospheres. It also covers breathing gas for hyperbaric operations and synthetic air. While EN 12021 does not cover aerospace applications, the British MOD publication DEF STAN 68-284 and its counterparts in other countries cover also the breathing gases used in aviation.