Diving with nitrox, or enriched air nitrox (EANx) is technically more correct, means that the gas mix inside the scuba cylinder contains a determined percentage of nitrogen and oxygen.
The principle reason certified scuba divers choose to increase the oxygen rich content in the tank is to extend the time they can stay submerged at certain depths.
The benefit of nitrox dives is absorbing less nitrogen and at a slower rate into your body tissues which in usually results in longer 'no decompression limits' often called divers' bottom time.
Nitrox safety guidelines and procedural standards for professional and recreational divers state that the mixture of nitrogen and oxygen gases must follow certain requirements.
Generally, the amount of enriched oxygen gas is above 21% found in regular air mixes up to a maximum 40% of the total gas volume. The most common dive mixes are 32% and 36% oxygen.
Using a higher percentage of oxygen richness obviously means that the nitrogen content is less than in typical air dives. For example, a regular filled scuba tank contains close to 21% oxygen and 79% nitrogen.
If you increase the amount of oxygen to 32% then the nitrogen content is lowered to 68%.
The affect of less nitrogen absorption generally means the diver has a longer dive time before reaching his NDL's.
Since nitrogen gas absorption is directly related to the risks of developing decompression sickness, enriched air nitrox is the preferred choice for multi-day or repetitive dives.
Not all divers benefit from using nitrox. If you intend to dive with enriched air you need to train how to use it safely, you should complete the nitrox specialty certification course which educates divers to the additional risks of oxygen toxicity and how to use oxygen specific nitrox scuba equipment.
Training to dive with enriched air nitrox requires understanding of specialized compatible gear such as enriched air dive tables or a nitrox dive computer. You also learn how to identify equipment markings for diving with increased oxygen contents such as nitrox tank filling and using oxygen analyzers.
Article Submitted 2012 by Scuba Steve