Nitrox is an oxygen-enriched breathing gas that can give you more no-decompression time at a given depth. I recommend considering it if you’re doing several dives a day or diving over several days, especially on a liveaboard. I choose it whenever it’s available on our dive holidays, but understanding its limits matters.
What is nitrox?
In recreational diving, when we talk about nitrox, we usually mean enriched air: a mixture of oxygen and nitrogen containing more oxygen than the approximately 21% in ordinary air. Increasing the oxygen percentage reduces the nitrogen percentage. That change is what gives nitrox its main diving benefits.
Two common blends are 32% and 36% oxygen, often written as EAN32 and EAN36. The number tells you the oxygen percentage, not how deep you can dive. PADI: What is nitrox?
Does nitrox let you dive deeper?
This is probably the biggest misunderstanding about nitrox. It doesn’t give you permission to dive deeper. Increasing the oxygen percentage actually makes the oxygen-related depth limit shallower. Oxygen becomes toxic when its pressure is too high, so every blend has a maximum operating depth that you must respect.
Maximum operating depth, or MOD, means the deepest you can use that particular blend under the oxygen limit you’ve planned. Oxygen toxicity can cause a seizure underwater, so this is a limit to take seriously. Your training and experience may impose a shallower limit as well. DAN: Nitrox
Choose the gas for the dive you’re planning, rather than choosing a depth because you’ve got nitrox in the cylinder.
What are the benefits of diving on nitrox?
The main benefit is less nitrogen uptake compared with air at the same depth and for the same time. That can give you a longer no-decompression limit, meaning more time before your dive plan requires mandatory decompression stops. It can also provide a more conservative margin when you keep your dives shorter.
There’s an important distinction here. You can use nitrox to extend your no-decompression time, or keep to a more conservative profile and reduce nitrogen loading. Using all the extra time doesn’t automatically give you a lower risk of decompression sickness, or DCS.
Nitrox doesn’t eliminate DCS, and it doesn’t replace sensible dive planning, controlled ascents or appropriate surface intervals. DAN: Factors contributing to decompression stress
It also doesn’t put more gas in your cylinder. A longer no-decompression limit is only useful while your gas supply and the rest of your dive plan allow it.
Who would I recommend nitrox to?
I recommend considering nitrox if you’re doing multiple dives in a day or diving over several consecutive days. Liveaboards and dive holidays are obvious examples. That’s where its extra no-decompression flexibility can be particularly useful, provided the blend suits your planned depths and you’ve completed the appropriate training.
If you’re heading away for a week of diving, I think nitrox is well worth looking into before you travel.
PADI identifies Enriched Air Diver as its most popular specialty. Here in New Zealand, my impression is that we’ve been a bit slower to take it up. I’d like more divers to understand what it offers and when it makes sense. PADI: Enriched Air Diver
I also recommend that older divers consider it as part of a conservative approach. Being a little kinder on ourselves certainly appeals to me. But age alone doesn’t automatically mean a higher DCS risk, and nitrox doesn’t replace looking after your fitness or getting appropriate diving medical advice. DAN Europe: Aging diver
Will nitrox make you feel less tired?
Personally, I find I feel less tired after diving on nitrox than after diving on air, particularly when I’m doing several dives. That’s my experience rather than a benefit I can promise anyone else. Research hasn’t established a reliable reduction in post-dive fatigue from switching to nitrox.
On our dive holidays, I always choose nitrox when it’s available and appropriate for the dives. We might be doing two or three dives a day for four or five days, and I find I’m less fatigued than when I dive on air.
That’s one of my reasons for choosing it. Your experience might be different.
Feeling less tired also doesn’t tell you that your dive was safer. Unusual or marked fatigue after diving can be a symptom of DCS and deserves medical advice rather than being dismissed as an ordinary tired afternoon. DAN: Air, nitrox and fatigue
What do you need to do before using nitrox?
You need appropriate nitrox training before using it independently. That training covers analysing your cylinder, understanding oxygen exposure and depth limits, and setting your dive computer for the gas you’re actually breathing. Having a cylinder labelled “nitrox” is only the beginning of those checks, not the whole process.
Before diving, personally analyse the mix, record and label it correctly, confirm its maximum operating depth, and set your computer to match. These are practical skills to learn properly, rather than picking them up halfway through a dive holiday. PADI: Nitrox training and checks
FAQs
Is nitrox pure oxygen?
No. Recreational enriched air nitrox contains oxygen and nitrogen, with a higher oxygen percentage than ordinary air.
Can I dive deeper on nitrox?
No. The oxygen percentage determines the blend’s maximum operating depth. More oxygen means a shallower oxygen-related depth limit.
Does nitrox prevent decompression sickness?
No. It can reduce nitrogen loading for the same dive profile, but DCS remains possible.
Is nitrox worth considering for a liveaboard?
Yes. I particularly recommend considering it for multiple dives each day and several consecutive days of diving.
Will I definitely feel less tired?
No. I find that I do, but research hasn’t confirmed it as a reliable benefit for everyone.
If you’re planning a dive holiday or wondering whether nitrox suits your diving, get in touch with Dive360. We’re happy to help you understand the benefits, limitations and training involved.