Enriched air nitrox is defined as a breathing gas blend with a higher content of which gas compared to air?

Enriched air nitrox is specifically defined as a breathing gas blend that contains a higher percentage of oxygen compared to normal air. Standard air is composed of approximately 21% oxygen and 79% nitrogen, while nitrox mixtures typically have oxygen levels exceeding this, such as 32% or 36% oxygen, with the remainder being predominantly nitrogen. This increased oxygen percentage allows divers to benefit from reduced nitrogen absorption, which can help in minimizing the risk of decompression sickness and extending bottom times.

The other gases mentioned, such as helium, nitrogen, and carbon dioxide, do not constitute the defining characteristic of enriched air nitrox. Helium is sometimes used in specific gas blends for deep diving but is not a component of standard nitrox. Nitrogen is actually found in higher concentrations in normal air, and while carbon dioxide is produced during respiration, it is not a gas that would define enriched air nitrox. Hence, the increase in oxygen content is what sets nitrox apart as a breathing gas blend.