Compared to air, nitrox has a higher concentration of:

The correct answer is that nitrox has a higher concentration of oxygen compared to air. Standard air consists of approximately 21% oxygen and 79% nitrogen, along with trace amounts of other gases. In contrast, nitrox is a mixture of nitrogen and oxygen where the percentage of oxygen is increased, typically ranging from 32% to 40%, depending on the specific blend (such as EAN32 or EAN40).

This higher concentration of oxygen is critical for divers because it allows for longer bottom times at certain depths than would be possible when using air. It also reduces the amount of nitrogen taken in, which can lower the risk of decompression sickness during ascents. Understanding the implications of oxygen concentration is essential for managing oxygen toxicity risks and planning dives appropriately when using enriched air nitrox.

In this context, since nitrogen, carbon dioxide, and helium are not increased in nitrox, they do not represent the primary attribute differentiating nitrox from regular air.