Types of diving · Self-contained diving · Nitrox diving

Diving with a combination of gases involves using a means of respiration different to that of just air, the gas usually used on dives. Of all the possibilities available, the one with greatest acceptance among divers is the use of nitrox combinations or enriched air (Enriched Air Nitrox), whose name was invented by the NOAA (National Oceanic and Atmospheric Administration).

Nirtox is simply a combination of oxygen and nitrogen. The air is made up of approximately 21% oxygen and 79% nitrogen. Nitrox or EANx are commonly used terms to refer to oxygen-nitrogen combinations containing more oxygen than there is in ordinary air; that is, more than 21%. There are two standard combinations: Nitrox I, with 32% oxygen and 68% nitrogen, and Nitrox II, with 36% oxygen and 64% nitrogen.

The main advantage of diving with enriched air is the reduction of nitrogen in the gas inhaled. The nitrogen absorbed by the body during a dive is what places the diver at risk of suffering from decompression illness (Bend). Reducing the amount of nitrogen a diver breathes reduces the risk of having these sorts of problems.

By using Nitrox, dive times can be extended. Given that the no decompression limits are based on the absorption of the nitrogen, less nitrogen means greater time at the bottom. Some divers claim that they have felt less tired after diving with Nitrox (compared with similar dives using air).

Given that oxygen can be toxic at partial pressures of around 2 atmospheres, the Nitrox diving (which uses a greater amount of oxygen than air) can be dangerous at certain depths. Nevertheless this risk can be handled simply by respecting the maximum depths allowed for each combination.

Another risk related to Nitrox (which is also due to the larger concentration of oxygen involved) is that, if handled inappropriately, it becomes an inflammable substance. For this reason, the cylinders and valves used must be continually cleaned and checked by competent persons.