Gear & Skills
What Is Nitrox?
The blue-banded tanks you see on dive boats, what enriched air actually does for you, and what it doesn't.
Nitrox, also called enriched air or EANx, is breathing gas with more oxygen and less nitrogen than ordinary air. Less nitrogen means you can stay longer at typical recreational depths before reaching your no-decompression limit, and many divers feel less tired afterwards. The trade-off is a shallower maximum depth, because the extra oxygen becomes a hazard deeper down. It needs a short specialty course, usually with no extra dives required.
- What it is
- More O2, less nitrogen
- Common blends
- EAN32 / EAN36
- Main benefit
- Longer no-stop time
- Main limit
- Shallower max depth
Spend time on a dive boat and you will see tanks with green-and-yellow 'NITROX' bands, and divers who swear by them. Here is what enriched air actually does, in plain terms.
Air vs nitrox
The air we breathe is about 21% oxygen and 79% nitrogen. Nitrox simply increases the oxygen and reduces the nitrogen. The two most common recreational blends are EAN32 (32% oxygen) and EAN36 (36% oxygen). Since nitrogen is what loads up in your body and limits your dive time, breathing less of it has a clear benefit.
What nitrox does for you
- Longer no-decompression limits. With less nitrogen going in, you reach your no-stop time more slowly, so you can stay down longer at the same depth, which is wonderful for second and third dives of the day.
- Shorter surface intervals. Less nitrogen loading can mean less time waiting between repetitive dives.
- Possibly less fatigue. Many divers report feeling fresher after nitrox dives. The evidence is mixed, but the comfort is real for a lot of people.
A common myth: nitrox does not let you go deeper, and it does not make your air last longer. You still breathe the same volume of gas, so your tank empties at the same rate. The benefit is more bottom time before your no-stop limit, not more breaths in the tank.
The catch: a shallower depth limit
Oxygen, helpful as it is, becomes toxic under enough pressure. That sets a maximum operating depth (MOD) for each blend, beyond which the oxygen partial pressure gets too high. As a rough guide, EAN32 has an MOD around 33 metres and EAN36 around 29 metres, shallower than the 40-metre recreational limit on air. You always analyse your tank and confirm its MOD before diving. This is exactly the kind of limit the dive computer and your training help you respect.
Do you need a course?
Yes, a short Enriched Air specialty. It is one of the most popular specialties precisely because it is quick, often classroom or online only with no required dives, and immediately useful. You learn to analyse the oxygen content of your tank, set your computer correctly, and calculate your maximum depth. After that, nitrox becomes a simple, routine part of diving.
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Get the Diving Standard appFrequently asked questions
What is the benefit of diving with nitrox?
Nitrox has more oxygen and less nitrogen than air, so you absorb nitrogen more slowly. That extends your no-decompression time at recreational depths, can shorten surface intervals, and leaves many divers feeling less tired.
Does nitrox let you dive deeper or stay down on one tank longer?
No on both counts. Nitrox actually has a shallower maximum depth than air because of oxygen toxicity, and you breathe the same volume of gas, so your tank lasts the same. Its real benefit is more bottom time before your no-stop limit.
Do I need a certification to use nitrox?
Yes. You take a short Enriched Air specialty course, often with no required dives, that teaches you to analyse your tank's oxygen content, set your computer, and calculate your maximum operating depth.