Safe upper limits for oxygen enrichment of room air at high altitude.

Oxygen enrichment of room air at high altitude has been shown to improve mental performance, sleep quality, and work capacity. Until now, the usual strategy has been to use an oxygen concentration that reduces the equivalent altitude to about 3,000 m, where the equivalent altitude is that which gives the same inspired PO2 during air breathing. However, standards adopted by the National Fire Protection Association allow considerably higher oxygen concentrations without introducing a fire hazard. For example, by raising the oxygen concentration to 31.5% at an altitude of 5,000 m, the equivalent altitude can be safely reduced to less than 2,000 m. At the extreme altitude of 8,000 m, the equivalent altitude can be reduced to less than 4,000 m without increasing the fire hazard. These increased levels of oxygen enrichment are feasible in practice using oxygen concentrators. They may be useful if lowlanders need to ascend rapidly and stay at high altitude, or for treating people with high altitude illnesses.