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Definition of Air
When a diver uses the term “air”, they mean … ![](https://previews.123rf.com/images/aneese/aneese1607/aneese160700726/61157632-scuba-tanks-lined-up-ready-for-a-dive-.jpg)
Air is the invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and nitrogen. Air is generally comprised of approximately 78% Nitrogen, approximately 20.9% Oxygen, and the balance of the trace gases including carbon dioxide and argon. Water vapor, while a variable, can be found in air as well.