The Aquanauts Guide to Nitrox Diving (A.K.A Diving With Enriched Air)

February 21, 2023 3 min read

rack of diving cylinders with nitrox labels on a dock next to the ocean

What is Nitrox Diving? 

When we dive with regular compressed air, the air in our tanks is comprised of 79% nitrogen and 21% oxygen. The nitrogen in the air, when under the pressure of water, can potentially be harmful to our bodies. This is because water pressure increases the partial pressure of gases, meaning the deeper we go, the more nitrogen that  gets saturated into our bodies. Our no-decompression limit, or no-stop time, is how long we can safely stay at a certain depth before we risk our bodies becoming overly saturated with nitrogen, which can cause decompression sickness. 

Enriched air nitrox is any air with a blend of more than 21% oxygen. If air has more oxygen, it contains less nitrogen, meaning that less nitrogen dissolves into our bodies as we dive. This means that when diving with enriched air at any depth, our no-decompression limit will be larger, i.e. we can stay at that particular depth for longer, without risking becoming overly saturated with nitrogen and developing decompression illness. With less nitrogen and longer no-stop limits, diving with enriched air also provides shorter surface intervals, as we need less time to off-gas. In addition, nitrox diving allows us to do more repetitive dives in a day, for the same reason. 

The Dangers of Breathing Oxygen at Depth

On the surface, breathing 100% oxygen is safe, and is in fact the treatment for decompression illness. However, the weight of the water increases pressure and this has an effect on the partial pressure of gases. The deeper you dive, and the more oxygen in your enriched air blend, the higher the oxygen partial pressure. The high oxygen partial pressures you experience with enriched air must be kept within limits to avoid oxygen toxicity, which can be a serious hazard. The higher the partial pressure, the less time you can safely be exposed to it. Unsafe exposure can lead to oxygen toxicity, the effects of which can lead to serious harm and death. 

The PADI Enriched Air Course

The PADI Enriched Air Course teaches you how to plan your dives with enriched air to stay well within the safety limits for oxygen exposure. With the guidance of your instructor, you will plan enriched air dives, using the Recreational Diving Planner tool and/ or dive computer in nitrox settings. You will also learn how to analyse your own tank to know how much O2 is in the air and to what depth you can safely dive with enriched air. It is imperative that you always analyse your own tank when nitrox diving - to help with this, most good scuba diving shops will sell an oxygen analyser to take with you wherever you dive! Some scuba diving centres will offer a dive with nitrox as part of the enriched air course, however this can also be completed as a dry course.

Misconceptions Busted! 

‘Diving with enriched air gives me a longer dive’ 

Not necessarily! When nitrox diving, the amount of air you have in your cylinder will not change. The benefits of diving nitrox are longer no-stop times, shorter safety stops and longer bottom time on repetitive dives. If you are someone who breathes on the heavy side, nitrox will not change the amount of air you consume on a dive. 

‘Nitrox diving is safer’ 

As mentioned previously, nitrox contains a higher percentage of oxygen, which at depth can also be fatal. One of the symptoms of oxygen toxicity is convulsions, which, if they occur underwater, carry a high risk of drowning. So, whilst higher oxygen does reduce our risk of decompression sickness, nitrox diving also carries its own set of risks, which the PADI Enriched Air Course will prepare you for.

‘Nitrox allows me to dive deeper’ 

Diving with air that contains more than 21% actually means you need to dive shallower than with regular air. Higher partial pressures of oxygen can be fatal, so we cannot dive too deep with nitrox - if you want to dive deeper than 30 metres, air is the safer option. 

‘Diving with Nitrox Makes me Feel Better’

Whilst some swear that breathing enriched air makes them feel better or ‘fresher’, it is not true for every person. The best way to feel fresher when diving is to get plenty of sleep, drink plenty of water, and work on your breathing techniques and buoyancy. 

If you have any further questions about nitrox diving, or would like more information on how to try it out for yourself, please don’t hesitate to get in touch with our experienced team of divers at Aquanauts.

Lizzie Chapman
Lizzie Chapman



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