Air — What It Is and Why It Matters
In scuba diving, air refers to the standard breathing gas composition of approximately 21% oxygen and 79% nitrogen. It is the most common and least expensive breathing gas, suitable for recreational dives to the standard 40-meter (130-foot) maximum depth. Compressed air is filled into scuba tanks using specialized high-pressure compressors with filtration systems.
The main limitations of air are nitrogen narcosis at deeper depths and relatively high nitrogen loading compared to nitrox. For these reasons, technical divers use enriched air nitrox for shallower portions of deep dives and switch to trimix for depths below 40 meters.
Frequently Asked Questions
Is compressed air in a scuba tank different from normal air?
It is the same atmospheric air, just compressed to high pressure (200 to 300 bar) and filtered to remove moisture, oil, and contaminants. The oxygen and nitrogen percentages are the same as what you breathe at the surface.
Why would I use something other than air?
Enriched air nitrox (higher oxygen, lower nitrogen) extends no-decompression limits at moderate depths. Trimix (adding helium) reduces narcosis and oxygen toxicity risk on deep dives. Both require additional training and certification.
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