What is "enriched air"?

Enriched air, often referred to as "nitrox" in diving terminology, is a gas mixture that contains a higher concentration of oxygen than the standard atmospheric air, which is composed of approximately 21% oxygen and 79% nitrogen. The primary characteristic of enriched air is that it typically contains between 22% and 40% oxygen, making it a preferred choice for recreational diving. The increase in oxygen offers divers several benefits, including longer bottom times and reduced nitrogen absorption, which can help mitigate the risk of decompression sickness during dives.

The other options describe gases or mixtures that do not fit the definition of enriched air. Pure oxygen (mentioned in the second option) is used in specific scenarios, such as for deep dives or as a safety gas in decompression scenarios, but it isn't considered enriched air. Technical diving mixtures involving argon and nitrogen do not pertain to the classification of enriched air. Finally, the term that references all types of diving gases is too broad and nonspecific to accurately describe enriched air. Therefore, the first option is the only one that correctly defines what enriched air is.