Breathing Gases For Scuba
Main article: Breathing gas See also: Air, Nitrox, Trimix (breathing gas), Heliox, and Decompression (diving)Until nitrox was widely accepted in the late 1990s, almost all recreational scuba used simple compressed and filtered air. Exotic gas mixtures presently used in scuba are intended to prevent decompression illness and nitrogen narcosis.
Some divers use nitrox, which usually has a higher percentage of oxygen, often 32% or 36% in EAN32 and EAN36, respectively. This lets them stay underwater longer for the same decompression requirement as for air, because less nitrogen is absorbed into the body's tissues. The drawback to the higher oxygen content is that at higher than normal partial pressures, oxygen becomes toxic, so scuba divers limit their exposure to partial pressures of less than 1.6 bar, by limiting the maximum operating depth for the mixture.
Open-circuit scuba sets may supply various breathing gases, but rarely pure oxygen, except during shallow decompression stops in technical diving.
Read more about this topic: Scuba Set
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