What is Nitrox? Why Should I Use It?

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Diver using Nitrox

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.

Nitrox tank, diver making the markings of the correct percentage.

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. Through this article, nitrox and EANx will be used interchangeably.

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

Nitrox Chart comparing atmospheric air versus enriched air

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?

Underwater closeup of divers mask surrounded by air bubbles


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.

SCUBA tank of pure O2

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.

Nitrox Certification

Nitrox diving is a bit more technically advanced than standard open water diving. Though the benefits of EANx are myriad, we thoroughly recommend getting at least your Advanced Open Water before you start thinking about nitrox certifications.

To dive with nitrox, you absolutely need to be certified. As with all types of scuba diving, without sufficient training, it can be incredibly dangerous. EANx diving requires more planning and technical knowledge – yes, this means more maths!

The PADI Enriched Air Diver course teaches you how to safely manage nitrox and correctly plan a dive with EANx. 

On a scuba diving safety stop

TDI’s Advanced Nitrox and Decompression Procedures course builds on that course and includes multiple mixes and deeper dives and teaches you how to safely manage oxygen levels and how to correctly plan the longer dives and shorter surface intervals you can execute with EANx.

Most dive computers also come with support for nitrox and allow you to input your blend. This is also true of the best air-integrated dive computers which allow multiple mixes on a single dive!

What’s The Nitrox Course Like?

The nitrox course with PADI is all classroom work with no required dives as diving with EANx requires no additional in-water skills. This is because it doesn’t feel or taste any different than a normal dive!

The class usually takes 3 to 4 hours, not including book work. They will go over all the calculations, how to analyze tanks, and go deeper into the physics of partial pressures of gases.

For the class, it is a great idea to bring your computer so you can have your
instructor teach you how to set your computer for diving with EANx.

Should I Get Nitrox Certified?

Diver using Nitrox

The decision to get nitrox certified is a personal one that usually hinges of specific things you wish to do.

If all your dives are at 18m or below and you’re content with that, the nitrox certification is unlikely to be worth the money. Just enjoy the shallower dives and work on your air consumption!


If you’re planning a liveaboard to some of the best scuba diving locations in the world, diving on nitrox is a great idea. You can reduce your surface intervals and you will feel less tired so you can make the most out of your trip! Whilst some liveaboards offer nitrox courses onboard, it is best to do the book learning before you go. Nobody wants to spend their trip-of-a-lifetime studying!

la galigo liveaboard sailing alone the coastline

Sometimes, getting a nitrox certification can be a good idea for a specific dive site. Some wrecks, like the Zenobia in Cyprus’ Larnaca Bay, sit at a depth that would limit your dive time due to no-decompression limits. By investing in nitrox, you can extend your bottom time and fully explore the site!

Another great reason to get your nitrox certification is to develop your scuba diving skills. It can help you deepen your understanding of the physics and broaden your scuba knowledge in general. And you have another shiny card to add to your collection!

So if you’re interested, talk to your local dive shop to get signed up to a class!

Nitrox Diver exploring underwater debris

Buying Nitrox

If you’re diving at a dive center, it is unlikely that you will have to fill your own tanks!


If you wish to dive on nitrox and have you own tank, you can walk into a dive shop and ask for a specific blend, assuming they have the capabilities. You’ll be expected to say what percentage blend you need (the x in EANx).

four nitrox compressed air cylinders

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. It’s a good idea to always plan ahead for your dive so you’re not disappointed!

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. 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 MOD (maximum operating depth), your nitrox certification number, and your signature. As a qualified nitrox diver, you will be expected to calculate your own MOD.

analox oxygen analyzer on white background

Does Nitrox Require Specialized Gear?

Nope! Well, except scuba diving gear…


The most important thing, especially when buying EANx is to make sure that your tanks are regularly serviced as dive shops will check and can refuse to fill your tanks if they’re not satisfied.

The time spans of services differ depending on location, but a good rule of thumb is that a tank needs:

  • Visual inspection every year – yep, they just open it up to check for water, rust, cobwebs… Or anything else that shouldn’t be there!
  • Hydrostatic test every 5 years. You can check out what this entails in the video below!

Today, most regulators are made to cater to all mixes of recreational nitrox – phew! 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, this is probably a good moment to get one. It makes diving on nitrox a lot safer and a lot easier!

Most modern dive computers have an EANx mode. This means that you can enter the specific EANx mix you are using into the computer’s algorithm. This will help you track your no-decompression limits and make sure that you’re not risking oxygen toxicity by nearing your MOD.


Well, maybe not so fun! If you have a drysuit, it’s important to make sure that you have proper drysuit undergarments. This is because some materials that are not designed for scuba usage can catch fire due to the increased percentage of oxygen! Even underwater, that’s a bad day…


You should now know a lot more about what nitrox is, what it does, and how it can be used. You will also know what certifications you need to operate safely with enriched air – and how to buy it at your local dive center!

Being able to dive with nitrox opens up more types of diving and helps to deepen a divers’ understanding. Oh, and you get a hefty dose of kudos!

Safe diving and happy bubbles!

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