What kind of gas mix is created by adding oxygen to regular air for diving?

The correct choice refers to the process of increasing the oxygen content of regular air, which is primarily composed of about 21% oxygen and 79% nitrogen, to create a gas mix characterized by a higher percentage of oxygen. This gas mix is commonly known as enriched air, specifically in the context of diving when the oxygen concentration exceeds that of regular atmospheric air.

Enriched air is particularly advantageous for divers because it extends bottom times and reduces nitrogen absorption, thereby minimizing the risk of decompression sickness. The most common enriched air mixture used in recreational diving contains between 22% and 40% oxygen. This specialization is essential for divers to maximize safety and efficiency during underwater activities.

In contrast, the other terms listed represent different concepts: trimix refers to a gas mixture containing helium alongside oxygen and nitrogen, hyperoxic air is a general term for air with higher-than-normal oxygen levels but is not specific to diving, and carbonated air typically pertains to gas dissolved in a liquid, which is not relevant to diving practices. The distinction highlights the importance of understanding gas mixtures and their applications in underwater environments.