Introduction to breathing gas at increased pressure

Breathing air at increased pressure, such as with self-contained underwater breathing apparatus (scuba) diving, introduces a complex series of hazards related to the increased partial pressure of the individual gas components. Nitrogen narcosis and oxygen toxicity occur while breathing compressed gas and resolve rapidly once a person is breathing gas at normal atmospheric pressure.

The complexities of gas mixtures and relative toxicities highlight the need for divers to have the mental ability to understand their equipment and environment well.