Enriched Air Nitrox

The following should allow anyone who is either unfamiliar with Nitrox, or confused by the terminology, to reach a point where they can follow a discussion on the subject. It may also serve as a starting point for those who wish to learn about Nitrox.

The biggest question is "What is Nitrox?" Well, the air we breathe is Nitrox. Air consists mostly of two gases: Nitrogen (79%) and Oxygen (21%), and there are some trace gases that are also in the air, they exist in such small quantities that we can ignore them. Nitrox is also referred to as "Enriched Air" or air that has been enriched with Oxygen so that it has more than 21% of Oxygen - usually 22% to 40% - blends that are usually used in Recreational No Decompression Dives. But really, Nitrox refers to any Nitrogen-Oxygen gas-mix, including blends that have less oxygen than air. For the purpose of Technical Diving, you learn to use Nitrox gas mixes from below 21% to up to 100% - although the richer mixes are usually used only for decompression.

Although Enriched Air Nitrox is relatively new to recreational diving, military and research divers have been using it to extend their no decompression limits for over 50 years. In fact, the first recorded Enriched Air mix was recorded by Draeger as early as 1917. The United States Navy and British Royal Navy studied and used Enriched Air in the 1940's and the United States Oceanic and Atmospheric Administration (NOAA) have more than 20 years field experience with Enriched Air used by their research divers.

There is also the question of how do you name a Nitrox mix. To distinguish one blend of Nitrox from another, the diving community uses the abbreviation EANx (for "Enriched Air Nitrox") followed by the Oxygen content percentage. For Example EANx36 is a Nitrox blend that contains 36% of Oxygen and the balance (64%) of Nitrogen: you would read "EANx36" as "Enriched Air 36" or "Enriched Air Nitrox 36" if saying it aloud. The most two common blends used in recreational diving are EANx32 and EANx36.

Why do you want to use Nitrox? You can stay longer underwater! The primary application of Nitrox is that divers use it to extend the no-decompression limit beyond normal air no-decompression limits. Nitrogen dissolves into your body while you are breathing air under pressure. The longer and deeper you dive, the more Nitrogen you absorb. As long as you stay within reasonable limits, when you ascend and surface, your body eliminates the excess Nitrogen through normal respiration without any difficulties. If you exceed reasonable limits, the excess Nitrogen may form bubbles and cause Decompression Sickness (DCS). Dive tables and dive computers help you track time and depth and keep Nitrogen within reasonable limits. Enriched Air replaces some of the Nitrogen you breathe underwater with Oxygen, so that during your dive, you absorb less Nitrogen than you would be breathing normal air. Your body metabolizes and otherwise absorbs the extra Oxygen, so that, within the limits of the recreational enriched air diving, it doesn't contribute to bubble formation after a dive. This means that you have longer no decompression limits for each depth than if you do using air. How much longer, depends upon the Enriched Air blend you chose, with more oxygen providing longer no-decompression time.

You feel less tired after repetitive dives on Nitrox. Well, some might argue that it isn't true, but any instructor who works and completes 3 to 5 dives a day will tell you that they do feel a whole lot better when these are completed using Nitrox. The best way is to try it yourself, but beware that this is only noticeable when completing at least 2 dives in one day - as your body doesn't have to work as hard to flush the excess Nitrogen out of your system, you feel less tired.

People have a tendency to think Nitrox is dangerous and is meant to be used