What Is Nitrox? Enriched Air, Explained
Nitrox is one of the most popular diver specialties — and one of the most misunderstood. Here's what it actually does, and just as importantly, what it doesn't.
What nitrox is
Ordinary air is about 21% oxygen and 79% nitrogen. Nitrox — also called enriched air, or EAN — simply has more oxygen and correspondingly less nitrogen. A common blend is EAN32, meaning 32% oxygen. Less nitrogen in the mix is the whole point, because nitrogen is what limits your dive time.
The benefit: more bottom time
Because you're breathing less nitrogen, you absorb it more slowly, which extends your no-decompression limits and can shorten the surface intervals between dives. That makes nitrox especially valuable for repetitive diving — a day of three or four dives, for example, where nitrogen loading would otherwise cut your later dives short.
The trade-off: oxygen and depth
The extra oxygen isn't free. At depth, oxygen's partial pressure rises (Dalton's Law), and too much becomes a toxicity risk. So every nitrox blend has a maximum operating depth (MOD) beyond which it isn't safe to breathe. This is the key point most people get backwards: nitrox does not let you go deeper — it actually limits your depth more than air does.
Analyze and label every tank
With nitrox you personally analyze each tank with an oxygen analyzer, confirm the percentage, label it, and set that number into your dive computer before you dive. Never breathe a mix you haven't checked yourself — your depth limits and no-stop times depend on the exact blend.
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Frequently asked questions
What does EAN32 mean?
EAN stands for enriched air nitrox, and the number is the oxygen percentage. EAN32 is a blend of 32% oxygen and 68% nitrogen, compared with 21% oxygen in ordinary air.
Does nitrox let you dive deeper?
No — it's the opposite. The higher oxygen content means oxygen toxicity becomes the limiting factor, so each nitrox blend has a maximum operating depth that is shallower than air's. Nitrox extends your time, not your depth.
Why does nitrox give you more bottom time?
Because it contains less nitrogen than air. You absorb nitrogen more slowly, so your no-decompression limits are longer and your surface intervals can be shorter — a real advantage on repetitive dives.
What is maximum operating depth (MOD)?
The deepest you can safely breathe a given nitrox blend before the oxygen's partial pressure gets into a risky range. Richer mixes (more oxygen) have shallower MODs.
Do you need a certification to dive nitrox?
Yes. Diving enriched air requires a short specialty course that teaches you to analyze tanks, calculate limits and set your computer. It's one of the most popular and accessible specialties.