Used in Scuba diving. It is a a breathing gas consisting of air mixed with a higher percentage of oxygen than normal air (40% and above is not uncommon).
Using EANx means that the rate of nitrogen absorption into the body is reduced. So the length of time a diver can remain at depth without requiring decompression increases (115 minutes versus 55 minutes at 60 feet) and the risk of [decompression sickness]? is reduced by lowering the nitrogen levels within the diver's body tissues.
It is not a deep-diving gas mixture.