What is the composition of diving air commonly used for SCUBA diving?

The composition of diving air is primarily nitrogen and oxygen, closely mirroring the air we breathe at sea level. In typical atmospheric conditions, air consists of approximately 79% nitrogen and 21% oxygen. This mixture is safe and suitable for standard scuba diving because it adequately supports human respiratory needs while minimizing the risk of toxicity and other complications associated with higher concentrations of oxygen.

When divers descend underwater, the pressure increases, which can have physiological effects on how gases are absorbed and utilized by the body. The standard mixture used in recreational diving, therefore, remains the typical ratio of nitrogen and oxygen found in the atmosphere, allowing divers to breathe comfortably at various depths.

In contrast, other gas combinations listed, such as those featuring high levels of carbon dioxide or a significant addition of helium, are not suitable for standard recreational diving. High carbon dioxide levels can lead to respiratory distress, and while mixtures with helium might be used in specific technical diving scenarios to avoid nitrogen narcosis at great depths, they do not represent the typical composition of diving air.