All gases except oxygen will cause asphyxiation by displacing breathable air in an enclosed workplace. They should be used and stored in well-ventilated areas. Only oxygen will support life. The presence of these gases cannot be detected without instrumentation. Asphyxiation can be sudden or may occur slowly without the worker being aware of the situation.

Unless large quantities of inert gas are present, the problem is easily prevented by using proper ventilation at all times. Nitrogen should be vented outside to safe areas. Analyzers with alarms should be installed to alert workers to oxygen-deficient atmospheres. Constant monitoring, sniffers, and other precautions should be used to survey the atmosphere when personnel enter enclosed areas or vessels. When it is necessary to enter an area where the oxygen content may be below 19 percent, self-contained breathing apparatus or a hose mask connected to a breathing-air source must be used. A conventional gas mask will not prevent asphyxiation.

Most personnel working in or around oxygen-deficient atmospheres rely on the buddy system for protection. However, unless equipped with a portable air supply, a co-worker may also be asphyxiated upon entering the area to rescue an unconscious partner. The best protection is to provide both workers with a portable supply of respirable air. Life lines are acceptable only if the area is free of obstructions and one worker is capable of lifting the other rapidly and easily.