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As a scuba diver, you’ve almost certainly heard of nitrox. At the very least, you’ll recognize the distinctive green-and-yellow tanks.


What exactly is nitrox? Or EANx?! And should you use it?

Well, our handy beginners’ guide will walk you through what nitrox is, when it is used for and whether it’s time for you to get your certification!

Let’s dive in.

What is Nitrox?

Technically, nitrox 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’ve been diving nitrox this whole time!

Well, yes and no.

When we refer to diving on nitrox, we are referring to enriched air nitrox also referred to as EANx.

This indicates that the air is enriched, meaning it contains an oxygen content of greater than 21%.

Nitrox Chart


What Does Nitrox Do?

In order to look at what nitrox does, we need to look more closely at the gasses involved. Scuba divers learn about the effects of nitrogen and oxygen in the body during their open water course.


Nitrogen slowly absorbs into the tissues of your body over the course of a dive. In order to prevent the bends, we must take care to safely get rid of the nitrogen before it can expand and form bubbles in our tissues as we ascend. We do this by ascending slowly, incorporating safety stops, and using dive tables or dive computers to work out how long we can safely stay at depth.

With EANx, some of the nitrogen is replaced with oxygen. Because the percentage is lower, nitrogen is absorbed into our tissues more slowly.

The result?

We can stay down longer! We can also enjoy shorter surface intervals because of the reduced volume of nitrogen in our systems and some divers claim it makes them feel less tired.

Nitrox sounds pretty perfect, right?


The other component of nitrox is, of course, oxygen. People are often surprised to learn that oxygen is a highly toxic and corrosive gas.

As the ambient pressure increases, so does the partial pressure of gasses.  The partial pressure increases all effects of the gas on the body – including toxicity. Oxygen toxicity can cause convulsions and paralysis, which can lead to death by drowning.

Whilst an increase in partial pressure changes how nitrogen interacts with our bodies too, it is not toxic in the same way as oxygen. It becomes intoxicating rather than poisonous in an effect known as nitrogen narcosis.

Even on normal air (21% oxygen), scuba divers can only descend to around 56m before the symptoms of oxygen toxicity become dangerous. As the oxygen percentage gets higher in EANx, the maximum depth you can dive to gets shallower. At 36% oxygen (EAN36), your maximum depth would be 29m.


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
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 logbook 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 inspection 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!