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If you’ve been diving long enough, you’ve probably seen the green-and-yellow enriched air nitrox diver (EANx) tanks.


You’re not exactly sure what nitrox or enriched air diving is useful for.

That’s where Scubaotter comes in.

After reading this ultimate guide to nitrox, you’ll know:

  1. What nitrox is.
  2. What nitrox is used for.
  3. How to get certified for nitrox diving.
  4. How to buy and fill tanks with nitrox.
  5. What gear nitrox can be used with.

Enough of the introduction, lets jump right in!

What is Nitrox?

Nitrox (EANx) is the chemical name for a gas composed of both nitrogen and oxygen. If you remember from your open water class, the normal air we breathe is 21% oxygen and 79% nitrogen.

So you have been diving nitrox this whole time without even knowing it!

But that’s not what most divers are referring to when they say “nitrox” (except for the very pedantic ones, like myself).

They are referring to enriched air nitrox, a special mixture of oxygen and nitrogen, where the oxygen content is enriched.

For nitrox to be considered enriched air nitrox (EANx), it needs to contain an oxygen content that is greater than 21%.

Nitrox Chart

What Does EANx Do?

As we hopefully learned and remember from our open water scuba diving class, divers must manage the nitrogen that gets dissolved in our blood so we don’t get bent like a pretzel.

Here’s a relevant scene from 47 Meters Down.

What makes EANx special, is that we get to replace some of the nitrogen with oxygen, meaning less nitrogen gets dissolved in the blood.

Because we ongass less quickly, we get to stay down longer!

We also can have shorter surface intervals than our air-breathing counterparts because we ongassed less throughout the dive.

We know what you’re thinking… Nitrox is too good to be true.

Here’s the kicker.

Oxygen is a very corrosive gas, and as ambient pressure increases, you’re exposed to an increased amount of oxygen.

Nitrogen works the same way. As you go deeper your body takes on more nitrogen.

We can actually “overdose” on oxygen due to oxygen toxicity, and that can cause us to convulse underwater, which usually turns deadly.

Do I Need EANx Certification?

Absolutely, diving EANx requires much more planning and a bit more (dare I say) math.

The Nitrox and deep dive certifications teach you how to safely manage oxygen levels and how to correctly plan the longer dives and shorter intervals you can execute with EANx.

Most dive computers also come with support for nitrox and allow you to input your blend.

What Should I Expect When Buying EANx?

As your local dive shop tank sherpa, I can fill your tank with a nitrox mix that contains a greater percentage of oxygen. You’ll be expected to say what percentage blend you need (the x in EANx).

You’re expected to calculate this depending on how deep you expect to go (as to prevent oxygen toxicity).

You will commonly hear about two standard mixes – 32% and 36%. Referred to as NOAA Nitrox I and NOAA Nitrox II, these blends are very standard mixes and often banked by dive shops.

Banked mixes make it quick and easy for you to fill your tanks with air.

If your mix isn’t banked, it may take over eight hours to mix your nitrox. Always plan ahead for the event that your blend isn’t banked by your local dive shop.

When it comes time to pick up your tank, you’ll be asked to analyze your tanks to determine the percentage of oxygen in that tank with an oxygen analyzer and label it.

Oxygen Analyzer for nitrox

It’s common and best practice to analyze them just before you dive as well.

You’ll then be asked to fill out a log book where you state the percentage of oxygen, the depth you may take it to without a high risk of oxygen toxicity, your nitrox certification number, and your signature.

Don’t forget to bring your card to the dive shop!

Does EANx Require Specialized Gear?

Maybe, maybe not, but you will need to get your tanks checked.

Scuba tanks are the pickiest thing when it comes to servicing gear. Hydro every five years, a visual inspection every year, etc.


It doesn’t get better with nitrox.

EANx has a greater percentage of oxygen, and oxygen is very corrosive, we need to make sure your tank is clean enough to put EANx in. Your visual inspections sticker will usually notate this.

If it’s not clean enough, it doesn’t mean you can’t have nitrox in that tank, it just means it needs to be cleaned.

Most regulators today come ready for all mixes of recreational nitrox. So, your regulator will probably work. If you have any questions about that, ask your local dive shop or your nitrox instructor.

If you don’t have a dive computer yet, now is when you should get one.

Most computers today have an EANx mode where you can put what EANx mix you are using into the computer and it will help you track your extended no decompression limits and make sure you don’t tox out on oxygen.

If you have a drysuit, make sure you have proper drysuit undergarments, because some material that’s not designed for scuba can catch fire due to the increased percentage of oxygen.

What’s The EANx Class Like?

Its all classroom work, and it has no required dives! Diving with EANx requires no extra in-water-skills. It doesn’t feel any different (although some may argue it does), it doesn’t taste any different, and you don’t change any of your skills because you are diving with EANx.

The class usually takes 3 to 4 hours, not including book work, and they will go over all the required calculations, how to analyze tanks, and go deeper into some of the things this article talked about.

If you do take the class, bring your computer so you can have your instructor teach you how to set your computer for diving EANx.

Padi Nitrox Certification

Should I Get Nitrox Certification?

If you are diving locally, the extra cost of EANx over air usually isn’t worth it. For example, if most of my diving happens within an hour of my house, so I have done the site more than a few times.

I don’t mind the limited no decompression limits a lot of the time as I can get a dive in within my air limits because I know the sites and work on my air consumption.

Having a shorter surface interval doesn’t bother me too much either, as I can just go get a sandwich after a safety stop.

If I’m spending money on a top dive location for only a few dive days, I want to get as much diving in as I can. So having the shorter surface intervals and being able to spend more time in the water is a big deal to me.

My recommendation would be to either just take the class to get it out of the way or wait until you have a vacation planned to take it.

Talk to your local dive shop to get a class signed up, and deck all your stuff out with that flashy green and yellow!


At the end of the day, being able to dive with EANx is something any serious diver should be able to do because it opens up so much more diving.

  • Nitrox (EANx) is a special mixture of oxygen and nitrogen, where the oxygen content is increased.
  • More Oxygen = Less Nitrogen. Less nitrogen is now dissolved in the blood causing you to ongass less quickly. This equals more bottom time and shorter surface intervals.
  • When purchasing Nitrox from a dive shop, you're expected to know what blend you need. If your blend isn't banked, prepare for an 8 hour period for it to be created.
  • Due to the corrosive nature of oxygen, Nitrox tanks are required to be serviced more frequently.

Safe diving from the ScubaOtter team!