Diving with Nitrox

Contrary to popular belief, Nitrox isn't to diving what Nanotechnology is to science. Stripped of its state-of-the-art myths and attachments, Nitrox was actually put to use successfully as long ago as WWI has been tested in theory since the late 1800's.

Nitrox diving tables were published in 1979 by USA's National Underwater and Atmospheric Administration (NOAA). Though used widely by commercial and technical divers because it allows for extended bottom time, Nitrox has only recently become incorporated into the rest of the diving market. The many advantages of shallow water Nitrox diving are contributing to its rising popularity in the recreational diving arena.

What is Nitrox?

Nitrox refers generally to any pure mixture ratio of nitrogen and oxygen, not to be confused with Trimix: helium, nitrogen and oxygen.

Enriched Air Oxygen Nitrox (or EANx – the x being percentage oxygen) mixes contain more oxygen than air. Air itself comprises 78% nitrogen, 20.95% oxygen and 0.93% argon other trace gasses and 1% water vapour. Air can more or less be equalled to Nitrox in that it contains just under 79% nitrogen and 21% oxygen. Hypoxia (medical term referring to oxygen shortage in the body) literally means 'lacking in oxygen' thus Hypoxic Nitrox contains has less oxygen (less than 21%) than air.

Why dive with EANx?

The answer is simple - to extend bottom time, stay down for longer and enjoy the sites without the interruptive no decompression surface breaks. The technical nature of Nitrox does not necessarily just confine its use to deep dives. For example: if you do two 25m (83ft) dives, you will need the required 2hr 19 min surface time no decompression break, but if you do the same with Nitrox you don't require any surface time.

Nitrox usage depends on the Maximum Operating Depth MOD. The more oxygen, the shallower the MOD, and in recreational diving is commonly used between 20 and 40 meters. Remember that nitrogen has no actual use in the body and ends up accumulated in the tissues. This is what decompression schedules are based on. If the ratio of Nitrogen drops in the gas mix the accumulation in turn is lowered, and decompression issues reduce.

Nitrox has also been known to reduce the effects of lethargy after a dive, as well as barotrauma due to the higher levels of blood oxygenation from the oxygen ratio in the mix.

The role played by equivalent air depth (EAD) in Nitrox diving is in one of its basic operational principles. EAD refers to the narcotic effect of various mixtures containing nitrogen. Decompression obligations revolve around reducing the risk of unnecessary nitrogen absorption into the tissues. Therefore it's about keeping the amounts of nitrogen absorbed at a certain depth equal to that which would be absorbed at the same depth on an air dive.

It doesn't require a degree in rocket science to understand that breathing the incorrect mixture of air can be life-threatening. Understanding how this concept works and changes under the pressures of water is even more intricate. Therefore, diving with Nitrox is only to be undertaken guided by highly trained professionals who understand the risks, and follow the correct procedures to minimize the severe consequences of irresponsible usage.

The fact that Nitrox contains a less harmful (narcotic) nitrogen, does necessarily mean that it causes less narcosis. As the inventors discovered in the 1800's oxygen can also be narcotic – proving the point that combined with nitrogen, the concoction can be pretty harmful if not done correctly. In addition, it's important to note that diving with nitrox does not interfere with a diver being able to receive treatment in a decompression chamber. Oxygen doses, much like the 'recommended daily allowance' on the nutritional labels of food products, are measured in OTU's Oxygen Tolerance Units -with an oxygen RDA of 1440 OTU's. A maximum OTU in a chamber treatment session is 600, leaving ample reserve.

Nitrox dives require no equipment modification other than the diving cylinder with the correct mixture – (and a dive certification to use it!)