The air that we breathe consists mainly of?

The composition of the air that humans breathe is approximately 21% oxygen and 78% nitrogen, with trace amounts of other gases like argon and carbon dioxide. This specific combination is important for respiratory function and overall life on Earth, as oxygen is crucial for cellular respiration while nitrogen serves primarily as an inert filler gas that does not chemically react in the body under normal conditions.

Understanding this balance is essential for divers, especially when transitioning to enriched air nitrox, which alters the oxygen and nitrogen levels to reduce nitrogen absorption and increase the safety of dives. Knowledge of atmospheric composition helps divers appreciate the implications of higher oxygen levels found in nitrox mixtures.