Understanding Nitrox in Recreational Diving

What is Nitrox?

Nitrox refers to any gas mixture composed of nitrogen and oxygen. This includes atmospheric air, which is approximately 78% nitrogen, 21% oxygen, and 1% other gases. In scuba diving, the term "Nitrox" generally refers to gas mixtures with a higher oxygen content than air, such as Enriched Air Nitrox (EAN32 or EAN36). These blends reduce nitrogen absorption in the body, which can extend no-decompression limits and reduce surface interval times.

Do You Need a Nitrox Certification?

To use Nitrox, you need a specific certification from your training agency. While the course is mostly theory-based and doesn’t require dives, it’s essential to understand gas analysis, MOD limits, and oxygen toxicity risks before using Nitrox safely.

My First Experience with Nitrox

Was in Cozumel, Mexico. I noticed no difference in how I felt compared to air, but for a small extra cost, I knew I was reducing my nitrogen exposure risk. Since then, I choose Nitrox whenever it’s available and MOD-appropriate because the reduced nitrogen load is worth the minor cost increase. My default blend is EAN32.

Debunking Common Nitrox Myths

INCORRECT. Nitrox actually limits your maximum depth due to the risk of oxygen toxicity.

INCORRECT. Nitrox extends your no-decompression limit but does not increase your gas supply.

INCORRECT. Nitrox reduces nitrogen loading at all depths.

INCORRECT. No scientific studies confirm this.

INCORRECT. Air (21% O₂) is technically a form of Nitrox.

Why Use Nitrox?

The two main benefits of diving with Nitrox are:

Reduced risk of decompression sickness (DCS) due to lower nitrogen absorption.
Shorter surface intervals due to reduced nitrogen loading.

While these benefits make Nitrox valuable, it does not replace proper dive planning and gas management or fundamental diving skills.

When Nitrox Might Not Be Available

While I always choose Nitrox when available, some dive destinations or liveaboards may not offer it due to supply limitations, cost, or logistics. It’s always a good idea to confirm availability ahead of time, especially if you’re planning multiple repetitive dives.

Nitrox Analysis & Tank Labeling

To safely use Nitrox, divers should:

Analyze the gas using an O₂ analyzer.
Label the tank with key information:

Oxygen percentage (to a single decimal point)
Initials (recommended for personal verification)
Analysis date
Optional: Tank pressure and MOD

Place the label under the valve handle for easy visibility.

Always Verify Your Computer Settings

Before diving, always set your dive computer to match your analyzed Nitrox mix. The primary risk of an incorrect Nitrox setting is exceeding your MOD, which increases the risk of oxygen toxicity. Most dive computers allow you to set an MOD alarm to warn you before reaching your depth limit.

Maximum Operating Depth (MOD) Reference Table

MOD is determined using Dalton’s Triangle. If you’re unfamiliar with this, check out our Guide to MOD Calculations.

Oxygen % (EAN)	MOD @ 1.4 PO₂	MOD @ 1.6 PO₂
21% (Air)	185 ft	215 ft
32%	110 ft	130 ft
36%	95 ft	110 ft

Key Takeaways

Nitrox is not magic. It won’t let you dive deeper or extend your gas supply.
The biggest advantage: Reduced nitrogen absorption lowers DCS risk and shortens surface intervals.
Always analyze and label your tanks. Verification is your responsibility.
Set your computer correctly. Incorrect settings can lead to depth limits or oxygen toxicity risks.
If available and MOD-appropriate, Nitrox is always a great choice—it is always my choice.