Typical decal used on scuba cylinders containing Nitrox

Nitrox is a breathing gas consisting of oxygen and nitrogen (similar to air), but with a higher proportion of oxygen than the normal 20.9%.

Several other terms for the same exist: Enhanced Air Nitrox, Oxygen Enriched Air, Nitrox, EANx or Safe Air.

Nitrox is mainly used in Scuba diving to reduce the proportion of nitrogen in the breathing gas mixture. Breathing nitrogen at depth causes two problems : decompression sickness and nitrogen narcosis. Reducing the proportion of nitrogen by breathing Nitrox can have two benefits:

• reduces the risk of decompression sickness
• extends dive times without increasing the need for decompression stops

Nitrox with more than 40% oxygen is uncommon within entry-level recreational diving. The two most popular blends are EAN32 and EAN36 (also named Nitrox I and Nitrox II or simply Nitrox32 and Nitrox36).

Nitrox with 50% to 80% oxygen is common in technical diving as a decompression gas, which eliminates inert gases, such as nitrogen and helium, from the tissues more quickly than leaner oxygen mixtures eliminate them.

There are several ways of mixing Nitrox in a diving cylinder:

• Put pure oxygen into a tank and then fill with air to make the required mix
• Remove nitrogen from air with a special filter or membrane
• Have nitrox premixed industrially

Nitrox is not a deep-diving gas mixture due the increased proportion of oxygen in Nitrox: oxygen becomes toxic when breathed at high pressure.

Warning: Diving and handling Nitrox raises a number of potentially fatal dangers due to the high partial pressure of oxygen. Only oxygen-safe tanks can be used. One must be extremely careful when using partial pressure blending. Divers who dive too deep (depending on the mix, 20 to 35 meters) may suffer from oxygen toxicity.

See also

• International Association of Nitrox and Technical Divers
• CMAS
• PADI