What is Nitrox and Why Do Scuba Divers Use it?

Last Updated: June 2, 2022

Nitrox is also known as “enriched air” or “EANx” and is a combination of nitrogen and oxygen used in recreational diving that has a higher concentration of oxygen than air (more than 21%). By using enriched air many divers are able to dive for longer but at shallower depths.

In this guide I will cover everything you need to know about nitrox, how to dive using it and the pros and cons of using nitrox when diving.

What is Nitrox?

Nitrox goes by many names such as EAN, enriched air and EANx. However, they all refer to the same thing, a gas that is composed of nitrogen and oxygen where the oxygen makes up more than 21% of the overall composition.

By containing more than 21% oxygen, nitrox has a higher percentage of oxygen than the air we breathe, hence the name “enriched air”. The rest of the gas (79%) is then made up of nitrogen.

However, you are able to find different levels of oxygen in nitrox, starting at 22% and ending at around 40% for most recreational dives. You will need to undertake a course to be able to dive with nitrox, especially if you are planning on using a higher concentration of oxygen in your diving tank.

What is Nitrox Made of?

As its very name suggests nitrox is a combination of two gases: nitrogen and oxygen. However, what makes nitrox unique is the ratio of oxygen to nitrogen. In the atmosphere we experience 21% oxygen and the idea behind nitrox is to increase this percentage.

So, nitrox is made of a higher percentage of oxygen than regular air. However, there is not one set ratio.

On the market there is nitrox I and nitrox II which both contain a higher concentration of oxygen, but at different levels. Nitrox I contains 32% oxygen (and hence 68% nitrogen) and nitrox II contains 36% oxygen (and hence 64% nitrogen).

What is the Difference Between Nitrox and Air?

The thing that sets nitrox apart from regular air is how much oxygen this gas contains. Although we are perfectly fine to breathe 21% oxygen when standing on the shore, when we get into the water to dive it is a different story.

This is where the difference between nitrox and air really comes to the fore. Nitrogen can be very dangerous at high pressures as the gas can penetrate into our body and form bubbles when pressurized, so by increasing the percentage of oxygen in the gas mix we are consequently reducing the nitrogen levels and the likelihood of nitrogen narcosis.

You will probably notice that a lot of divers prefer to use nitrox rather than regular air just to be on the safe side. However, you will need to be certified before you are permitted to dive with nitrox.

Is it Worth Getting Nitrox Certified?

The answer to whether or not it is worth getting nitrox certified depends on what types of dives you want to complete.

For example, if you only want to complete very shallow dives then you will be perfectly fine to use regular air to dive as you will not be reaching any dangerous pressures where the use of nitrogen will become an issue for your health.

However, if you are planning on doing deeper or even technical dives then it is very important that you understand the risk of using a gas tank with a high concentration of nitrogen at these pressures. If you are completing semi-deep dives then yes, it is worth getting nitrox certified.

What will I learn getting nitrox certified?

During your training course one of the most important things that you will learn is the safety behind different gas combinations. This is to ensure that you are always aware of the correct equipment to bring for a particular dive to make the experience as safe as possible.

You will learn the dangers of having a gas container with a high concentration of oxygen, such as filling tanks where the pressure is greater than on the surface.

You will also learn how to check the percentage of oxygen in your tank yourself to ensure that you are diving with the right mix.

Once you are aware of the dangers of your equipment and are capable of checking its accuracy, you will then be taught how to calculate your dive. It is very important that you are aware of the limits and capabilities of your equipment to help keep you safe.

The training course will teach you how to calculate your dive time and the maximum possible depth, as these will now be different to if you were diving using regular air.

There are many different methods that your nitrox instructor may use to teach you how to calculate these values which might include a diving app, a computer program or diving tables. The exact method will be dependant upon your teacher.

Everything in the training course is theoretical as you will only need to learn the physics behind what is happening with the nitrox. In practice, you will not be able to notice any differences and there are no special requirements. Diving with nitrox is the same experience as diving with air.

Pros and Cons of Nitrox Diving

pros and cons of nitrox diving

Now let me go through the pros and cons of diving with nitrox to help you understand the benefits of becoming nitrox certified as well as the benefits of diving with regular air.

Pros of diving with nitrox

Many people will wrongly assume that by choosing to dive with nitrox over regular air you will be able to complete deeper dives, but this is not the case.

  • Longer Dives

The main benefit of using nitrox is that you can dive for longer.

When diving with regular air there are limits both on the time that you can be underwater and the depth of your dive. However, because the concentration of oxygen is higher in nitrox there is a reduced risk from the nitrogen that you are breathing in.

Nitrogen, when depressurized, can cause bubbles to escape from the gas itself and these bubbles are small enough, under pressure, to enter into your tissue and bloodstream, meaning that as you surface they will expand. When this happens it is called depressurization sickness or the bends.

In some cases, this reduction in nitrogen means that you can dive for twice as long as you would be able to with regular air (for dives at a depth of 50 feet). However, you will need to rely on your nitrox training to accurately calculate the no decompression limits of your dive.

  • Shorter Surface Times

Diving with nitrox also results in shorter surface times on your dive. Again, the reason for this is the reduction in nitrogen. Because nitrox has a reduced percentage of nitrogen it will take your body a lot less time to be able to expel the extra nitrogen from your system, meaning you can get back to your exciting dive.

  • Less Fatigue

One final advantage is still not scientifically verified, but commonly reported by many divers, and that is less fatigue. A lot of divers who use nitrox as opposed to regular air report feeling less fatigued after their dive.

Many believe that the reason for this is once more the reduced nitrogen. There are fewer microbubbles of nitrogen in your blood stream and this results in less stress when decompressing. However, this is still yet to be proven.

Cons of diving with nitrox

Although there are many advantages to diving with nitrox it is still important that you understand the disadvantages and dangers so that you can make an informed decision about the best gas mix for you.

  • Not for Deep Diving

One of the reasons why many people want to start diving with nitrox is that they think they will be able to reach greater depths, but this is not the case. Just like with normal air, nitrox has its depth restrictions. You will be able to dive for longer, not deeper.

Nitrox can be very dangerous to inhale beyond its maximum depth limit and this is due to the nitrogen in the gas which can have significant anaesthetic effects when pressurized. So, you will need to check your restrictions carefully when diving with nitrox to avoid becoming unconscious.

  • Oxygen Toxicity

The oxygen in nitrox can also cause issues because of oxygen toxicity. If you are spending too much time underwater breathing in the enriched air nitrox then you may start to notice the effects of oxygen toxicity.

There are no set consequences of oxygen toxicity but there are some key symptoms to look out for. These are distorted vision and convulsions. If you start to notice any issues then it is important that you resolve these as quickly as possible.

If you keep an eye on your depth to ensure that you do not exceed the maximum for your dive and your oxygen exposure then you should be able to avoid oxygen toxicity. If you do begin to convulse the make sure to keep your respirator in as this can easily lead to drowning.

Does Nitrox Improve Air Consumption?

No, nitrox does not improve your air consumption. This is actually a very common myth and on its surface it does sound plausible. After all, surely if you are breathing in more oxygen than normal you will need to take fewer breaths, right? Not true.

One of the main reasons why you will still breathe as frequently as you would on normal air actually has nothing to do with the oxygen levels in nitrox, but the carbon dioxide levels in your body. You will still need to expel just as much carbon dioxide as normal and so you will need to keep the same breathing frequency to expel this Co2.

Any extra oxygen that you get from the nitrox is simply dispelled from your body as unused oxygen, meaning that you are not making full use of the increased levels of oxygen in the nitrox.

Several studies have shown that the tiny increase in air consumption that you get from using nitrox is so insignificant that it is entirely negligible and makes no difference to the diver, so much so that you would never notice it.

How Deep Can I Dive With Nitrox?

nitrox calculator

The exact depth of your dive should be calculated using the proper tools. However, as a rough guide if you are diving with nitrox II (a mix containing 36% oxygen) then you will be able to dive down to a maximum of 100 feet. If you are using 32% nitrox then this maximum depth will increase slightly to 121 feet.

However, it is important to note that these are rough guidelines and you should always take into account your personal condition, experience and the length of time that you plan to spend below the surface.

Oxygen toxicity can occur even within the recreational diving range. So, in order to ensure your safety when diving you should never push your equipment to its limit.


Scuba diving is an incredibly exciting activity but it can also be a very dangerous one. For this reason, it is important that you are equipped with the right gear and that you have the appropriate training or at least you are with someone who does.

Nitrox is a great tool to have to allow you to explore for longer, but it is important that you also understand its limits and risks. Unlike the common myth, you cannot dive deeper using nitrox, only longer. Diving deep using nitrox can lead to the pressurized nitrogen becoming an anaesthetic, posing significant risks.

By becoming nitrox certified you will be made aware of all of the pros and cons of diving with enriched air as well as learn how to properly calculate your dives yourself, covering everything from dive time to maximum depths. Make sure that you are well aware of the signs of oxygen toxicity to have a safe dive.

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