Nitrox (Enriched Air)

A breathing gas with more oxygen and less nitrogen than air, most commonly EAN32 or EAN36, giving longer no-decompression limits at moderate depths.

Nitrox, or enriched air, is any nitrogen and oxygen mix with more than the 21 percent oxygen found in air. Recreational diving uses mainly EAN32 and EAN36, meaning 32 or 36 percent oxygen. Because less nitrogen enters your tissues at a given depth, nitrox extends no-decompression limits and can leave you feeling fresher on repetitive dives, which is why it is the default gas on many liveaboards.

The trade off is oxygen. Higher oxygen content means oxygen toxicity becomes the limiting factor, so every nitrox mix has a maximum operating depth: 33.7 m (110 ft) for EAN32 and 28.9 m (95 ft) for EAN36 at a PO2 of 1.4 bar. Nitrox divers personally analyze their tank before diving, label it with the measured percentage and MOD, and set their dive computer to the mix so it tracks both nitrogen and oxygen exposure.

Using nitrox requires a short certification course covering oxygen exposure and analysis procedures. Two myths are worth killing early: nitrox does not let you dive deeper, its MOD is shallower than air's practical limits, and it does not meaningfully change how long a tank lasts, since gas consumption depends on depth and breathing rate, not on the oxygen content of the mix.