Nitrox is a special breathing gas mixture that's available as an alternative to air. Nitrox is simply normal air that is blended with additional oxygen. This creates a breathing gas that contains less nitrogen and more oxygen than normal air.
Recreational Nitrox can be blended to contain as much as 40% oxygen. The most popular mixtures are EAN 32 and EAN 36. "EAN" stands for "Enriched Air Nitrox," and the number that follows indicates the mixture's oxygen percentage.
Benefits of Nitrox
Nitrox contains less nitrogen than standard air. This means that as you dive, your body ingasses less nitrogen than it would with standard air. As a result, you can spend more time at a specific depth without developing decompression sickness. The increase in bottom time depends on the oxygen percentage of the nitrox mixture.
Another benefit is reduced surface interval times. This is extremely beneficial when visiting deeper dive sites from a boat. The boat's schedule might not allow for extended surface intervals, which means divers using air may have to cut their second dive short in order to prevent exceeding their no-decompression limits. But with Nitrox, the reduced nitrogen ingassing reduces the required surface interval time between dives, which allows for longer repetitive dives.
Nitrox presents new hazards to divers, with the increase of oxygen being the main concern. The increase in oxygen results in shallower maximum depths, special equipment requirements, and additional dive planning.
To use Nitrox, you must complete a Nitrox specialty course. This course will teach you how to plan your dives, select appropriate equipment, and verify the oxygen percentage in your mixture. Most of this course involves classroom lessons, and dives may or may not be required for certification.
The most significant equipment requirement for Nitrox is a specially cleaned cylinder labeled for use with Nitrox. Another item that's nice to have, but not required, is a dive computer that's Nitrox compatible.