Gases with a fraction of oxygen greater than 0.21 are referred to as?

Gases with a fraction of oxygen greater than 0.21 are referred to as hyperoxic. In normal atmospheric conditions, the oxygen fraction is approximately 21%, which is considered normoxic. When oxygen levels exceed this percentage, the term hyperoxic is used to describe the increased availability of oxygen in the mix.

Hyperoxia can occur during scuba diving when divers use enriched air nitrox or other gas mixtures that provide a higher concentration of oxygen than what is available in air. This is significant for divers to understand as it can lead not only to benefits such as better nitrogen management but also potential risks like oxygen toxicity at greater depths and pressures.

This distinction is important for safe diving practices, as it emphasizes the need for divers to be aware of the gas compositions they are breathing and the implications associated with elevated oxygen levels while underwater.