Nitrox is any combination of oxygen and nitrogen. The air you breathe today is a form of Nitrox, which is 79% nitrogen and 21% oxygen. Nitrox mixtures with greater than 21% oxygen are referred to as Enriched Air Nitrox (EANx). The “x” refers to the percentage of oxygen in the mixture. The most commonly used Nitrox mixtures are EAN32 (32% oxygen and 68% nitrogen) and EAN36 (36% oxygen and 64% nitrogen).
Nitrox training involves taking a certification course from a training agency, such as SDI/TDI, NAUI, PADI, IANTD, or GUE. The training course teaches you how to safely use and apply Nitrox to your current diving ability and certification.
There are generally two Nitrox courses: Basic Nitrox and Advanced Nitrox. Basic Nitrox courses teach you to safely breathe and use Nitrox in the 40 to 130 fsw (12 to 39 msw) depth range. It teaches you the benefits of Nitrox, how to calculate the mixture percentages, the importance of using Nitrox mixtures at appropriate depths, oxygen toxicity, how to use Nitrox tables, as well as much, much more. The class also requires you to make several dives with an instructor using Nitrox.
Advanced Nitrox courses extend your understanding of oxygen and introduce you to using mixtures up to 50% oxygen for decompression. It also extends your knowledge of applying Nitrox to different diving requirements and builds your knowledge and understanding of advanced uses of Nitrox.