EAN (or EANx) is an abbreviation for enriched air nitrox, a mixture of oxygen and nitrogen used as a breathing gas in in scuba diving. EAN contains only nitrogen and oxygen. any other gasses are only present in trace amounts. The term "EAN" specifically denotes a gas mixture that has a higher percentage of oxygen than normal air (more than 21% oxygen); it is essentially air that has been "enriched" with additional oxygen. While EAN may contain any percentage of oxygen greater than 21%, the most common mixtures are EAN 32 (NOAA Nitrox I) and EAN 36 (NOAA Nitrox II) which are have 32% and 36% oxygen respectively. Special training and certification and required to dive with EAN.