What is nitrox used for in diving? - Is it safe?

what is nitrox for

Using nitrox in diving is an excellent technique that will allow us to enjoy a good balance by extending our limit without decompression stops and to explore the underwater world with greater peace of mind. 

However, certain techniques and instructions must be followed in order to use it, as it has several differences with air diving. In addition, as well as having advantages, it also has several disadvantages and some risks.

To expand on all this information, we have prepared a complete guide to learn the basics about the use of nitrox in diving. We also tell you which mixtures are recommended, the common mistakes to avoid and when it is really convenient to use this technique Dive with us!

What is nitrox?

It is also known as enriched air or EANx and consists of a mixture of gases used for diving (technical or recreational). In order to fulfil its function , it uses different proportions of oxygen and nitrogen than the usual air used, which would be 21% oxygen and 79% nitrogen.

The term "enriched air" is given to it because it contains more oxygen and less nitrogen, the proportions varying according to requirements.

Types of nitrox

Nitrox types are classified according to the percentage of oxygen they contain, which can range from 21% to 99%. However, in recreational diving, mixtures ranging from 22% to 40% are most commonly used, with 30% to 40% being the most common. 

However, as established in the diving community, the abbreviation EANx followed by the percentage of oxygen contained in the mixture is used to differentiate between mixtures.

For example, among the best-known mixtures are 3:

  • EAN32 or Nitrox I, which contains 32% oxygen and 68% nitrogen. It is suitable for recreational diving and can be used at any depth within the recommended recreational diving limit (which is 30 metres).
  • EAN36 or Nitrox II, with proportions of 36% oxygen and 64% nitrogen. It can be used for prolonged dives at moderate depths. If the depth is shallower, EAN36 will allow longer no-decompression bottom times. However, when approaching the recommended depth limit for recreational diving, there are risks due to the higher oxygen concentration. We will expand on this later. 
  • EAN40, which contains 40% oxygen and 60% nitrogen. The use of this mixture is outside of recreational diving, so if you are interested in reaching these limits be sure to ask a specialised instructor. 

What is the most recommended nitrox mixture for diving?

There is no standard mix that is better or worse when using nitrox in diving. Therefore, when planning, it is necessary to keep in mind that every dive is different and requires specific procedures. All these factors must be analysed to be within safe margins. 

To choose a suitable air mixture when diving with nitrox we must base our choice on the depth and the time we want to stay in the water. Therefore, beyond thinking about which is the best or worst, we must think about which is the right one for that particular dive. 

To do this, you will be guided by the safety limits that you must always keep in mind. 

Of course, you should always know the percentage of air you are diving with. Remember that an increase in the percentage of oxygen in your mix involves meeting several special guidelines. 

This will allow you to avoid accidents normally related to equipment and oxygen toxicity in your body. We will expand on this later. 

What is nitrox used for in diving and how does it work?

Nitrox diving basically consists of using these "altered" gas mixtures for our dives. However, to understand why, let's start by clarifying some essential points.

First of all, it is necessary to understand the effect of nitrogen on our body while diving. As a starting point we must take into account that, when we dive to a certain depth, the nitrogen that we are absorbing from the tank is dissolved in our body due to the effect of the pressure.

Therefore, as the depth and time of immersion increases, more nitrogen will be absorbed by the body.

Of course, if we stay within the established safety limits, that excess nitrogen will be expelled with our breath as we ascend to the surface.

However, if the safety limits are not respected, there is a risk of decompression sickness (DCS).

So, bearing in mind that what the body accumulates is nitrogen, what would happen if we reduce its levels in the mix?

By reducing the amount of nitrogen in the mixture, we also reduce its absorption, which gives us advantages compared to diving with air.

However, the most important benefit is the possibility to increase the bottom time at a given depth.

For example:

Let's suppose that when diving in Lanzarote we use an air tank with the typical mixture of 21% oxygen and 79% nitrogen.
This will allow us to dive to a depth of 18 metres for 56 minutes.

At the end of the dive the excess nitrogen will be naturally expelled by the body.

On the other hand, let's imagine that in this same situation we use a 32% enriched air mixture (EANx32). As in the previous case, we will be able to dive to 18 metres, but this time it will be possible to stay underwater for 95 minutes without going into decompression.

If we do a simple calculation, we will notice that we have managed to extend our diving time by up to 40 minutes, which is wonderful!

And how is all this achieved? Simple. When we increase the percentage of oxygen in the mix, the percentage of nitrogen is reduced. Therefore, the body will absorb lower levels of nitrogen and, as a result, will have more time available until the no-decompression limits are reached.

Enriched air for diving

By using nitrox in diving, do we avoid going into decompression?

No. All we achieve is to extend the time before entering decompression, but this phase is not avoided. However, if we exceed the maximum time, it will be necessary to make decompression stops. However, the latter is outside the limits of recreational diving, as these are practices that only apply to technical diving inthe practice of diving with enriched air nitrox.

Diving with nitrox and its advantages

Now that we know what nitrox is and what its function is in the practice of diving, it is time to delve a little deeper into the benefits it provides.

So here are the advantages of diving with enriched air nitrox:

✅ Improving safety

Due to the reduced levels of nitrogen in the mix, the risks of decompression sickness are also reduced, resulting in a higher overall safety rate when diving.

Remember that the nitrogen absorbed by the body is the main cause of this condition. For example, if we dive with air at about 30 metres for 15 minutes, we will be very close to the no decompression limit. However, if we use nitrox we will have a little more time and, therefore, we will be further away from that limit.

It is because of these situations that nitrox diving could be considered safer. Of course, this is only true if the safety limits are strictly adhered to.

✅ Increases background time

When using nitrox in recreational diving, the cylinder may contain between 21% and 40% oxygen, which indicates a lower percentage of nitrogen compared to when using conventional air.

These ratios allow divers to extend their no-decompression limits by reducing the amount of nitrogen the body absorbs. Recall that the less nitrogen there is in a diver's breathing mix, the less nitrogen absorption there will be at a given depth.

Surface intervals will be shorter.

As mentioned throughout the text, a diver using Nitrox will absorb less nitrogen for a given depth and dive time compared to one using air.

This will mean that the diver using nitrox will have less nitrogen to release in the surface interval required, and is therefore able to shorten them significantly.

We will be able to enjoy longer repetitive immersion times.

In case you are involved in more than one dive a day, diving with nitrox is extremely convenient. This is because you can extend the enjoyment time on each of your dives, which is particularly useful during dive trips.

In these cases, because there is less nitrogen accumulation, we can enjoy the underwater scenery to the fullest and safely. In contrast, when diving with air we will have to take time out of the dives to allow the high levels of nitrogen to be eliminated by our body. 

✅ Reduced exhaustion at the end of the dive

Many divers report that when diving with nitrox, the feeling of fatigue is noticeably less compared to diving with air. It is possible that this is due to the reduced absorption of nitrogen, as its accumulation in the body tissues often leads to the feeling of exhaustion. 

However, there is as yet no conclusive medical evidence to support this theory

Disadvantages of nitrox in diving

After learning about the advantages of nitrox in diving, it's time to find out what the disadvantages of nitrox are. Make sure you take them into account before your dive:

❌ Caution should be exercised with regard to the maximum depth

So far so good with the plus oxygen minus nitrogen ratio, but did you know that this could lead to oxygen toxicity?

The reason is that oxygen under pressure can be toxic. Of course, this will depend on the depth and the percentage of oxygen you use, so it is always advisable to follow the recommendations of an expert.

However, you should also be aware that this is a very occasional risk, especially if you are recreationally diving.

In this type of diving the most commonly used mix is Nitrox 32 (32% oxygen and 68% nitrogen) and its maximum operating depth (maximum depth to which we can dive with a particular mix) is approximately 30 metres.

❌ Special equipment required

Another point to bear in mind is that nitrox diving requires a tank specially designed for the use of enriched air. In addition to this, it will be necessary to carry an oxygen analyser, as you will be responsible for ensuring that the mixture on the marking label and the mixture in the tank are the same.

In general, the centres that offer the service for diving with nitrox usually provide this type of equipment, although always check beforehand to be on the safe side.

❌ Availability of nitrox

Although its use is becoming more and more widespread in the diving community, depending on the location you may find it difficult to find centres that offer you the opportunity to use nitrox for diving. In Lanzarote, for example, you will find the professionals at Titan Blue Divers, who will guide you through the whole process so that you can enjoy the experience to the fullest (and safely).

Enriched diving air

What are the risks of using nitrox in diving and how to avoid them?

It is vital to follow the relevant safety protocols for using nitrox for diving, as this will help us to avoid any risks as much as possible. However, a key step to ensure our protection is to know what dangers exist when practising this activity and how to avoid them. We will now tell you what they are:

Oxygen poisoning

This is the biggest danger we can face when diving with nitrox, so it is necessary to know about it and how it can be prevented.

First of all, you should be aware that this will only happen if you dive outside the limits, without respecting the maximum operating depth.

The partial pressure exerted on oxygen at a certain depth causes it to become toxic, affecting our nervous system. In these situations we run the risk of breathing oxygen at a partial pressure greater than 1.4 BAR.

As a direct effect of this toxicity , convulsions can occur, which, being underwater, represent a high risk of loss of regulator and subsequent drowning.

🟢How can this be avoided?

The first recommendation to avoid oxygen poisoning is to constantly monitor the depth at which we are diving. Similarly, a very efficient safety measure is to activate an alarm on our dive computer that alerts us about two metres before the maximum operating depth.

This gives you a safety margin of a couple of metres. It is also advisable to be alert to any symptoms that may predict if you are suffering from oxygen toxicity. These include abnormal vision, dizziness, lightheadedness, dizziness, trembling, ringing in the ears, euphoria and restlessness.

Therefore, if you experience any of these, ascend instantly and end the dive immediately.

Oxygen saturation

Nitrogen is not the only thing that can accumulate in the body while diving, as oxygen does too. For example, successive dives can cause burning in the lungs and other symptoms. However, if we dive successively, we may experience lung burn and other symptoms, This is unlikely to be the case, as our body has a high tolerance to oxygen accumulation. Therefore, to undergo oxygen saturation we should spend too much time underwater.

🟢How can this be avoided?

Most dive computers with nitrox mode come with an oxygen accumulation indicator.. Therefore, the recommendation is to be attentive to the indications that it shows us. There are also tables for calculating oxygen saturation in the body.. However, it is no longer done in this way in most centres, as dive computers are used.

Common mistakes when diving with nitrox

In addition to being aware of the dangers you may face when diving with nitrox, it is also important to know what the most common mistakes are when diving with nitrox. In this way, you can avoid making them and protect yourself from the risks involved. Find out about them right away:

Reading errors in the analysis

In order to know the mixture in a cylinder, it is recommended to do a preliminary analysis using an instrument known as an analyser.
However, if we fail the analysis and therefore calibrate the computer incorrectly , we run the risk of decompression sickness or oxygen poisoning.

🟢How can this be avoided?

The most effective way to avoid this is to know in depth how to do the analysis, what to avoid or what details to look out for. Therefore, a key step is to take a good nitrox diving course and to have professional instructors to guide you through each step.

Another key step is to confirm that the analyser is approved and has undergone regular tests to ensure its performance.

Computer calibration error

Avoiding this mistake is as important as not exceeding the depth limits, as we must ALWAYS calibrate the computer with the right mixture

For example, if we calibrate for Nitrox 36 and there is Nitrox 32 in the tank, it is quite likely that we will suffer from decompression sickness

If we do the opposite (dive with Nitrox 36 and calibrate for Nitrox 32) we run a serious risk of oxygen poisoning

🟢How can this be avoided?

There are two fairly simple ways to prevent this mistake. The first and most important will always be to take a Nitrox course in which we learn how to correctly analyse the gas mixture in our cylinder.

The other way to avoid this is to read the instructions on the computer, so that it is clear how it should be programmed for nitrox diving. 

Finally, don't forget that it is important to concentrate well when doing the analysis and preparing for the dive

When to use enriched air nitrox in diving?

Diving with nitrox can be quite convenient in the following cases:
  • On dive trips with several dives a day
Continuous diving increases the amount of dissolved nitrogen in our bodies. Therefore, whether we are travelling liveaboard or in resorts, it is best to use nitrox in diving to reduce the nitrogen load.
  • If we will be doing deep dives with numerous underwater attractions
For example, if you are visiting a wreck at a depth of about 30 metres. Chances are you will need a lot of time to traverse it, so nitrox can be a good ally.
When to use nitrox

What equipment should be used for diving with enriched air nitrox?

When discussing the equipment required for nitrox diving, it is important to consider a guideline used among equipment manufacturers. It states that for dives using oxygen mixtures of less than 40%, no modification is required.

Now, when using oxygen mixtures above 40%, equipment capable of withstanding such high oxygen levels must be incorporated.

The reason is that by using high amounts of oxygen, conventional material deteriorates much faster. It is also important to always follow the manufacturer's recommendations when using nitrox equipment.

Can anyone dive with nitrox?

No. Nitrox enriched air should not be used by every diver. The reason is that ignorance of specific rules and procedures when using nitrox can lead to serious complications. Therefore, prior training is required in order to be properly trained

It is always advisable to attend and pass a Nitrox specialty course taught by certified instructors. It is important to get your certification from a reliable dive centre that is authorised by globally recognised dive organisations (such as PADI).

What does the nitrox diving course consist of?

When you sign up for a nitrox diving course you will learn everything you need to consider when diving with nitrox, from oxygen exposure, safety, equipment, blending and more.

You will learn all the safety measures that you must apply to prevent accidents that may arise when practising this activity. In addition, the instructors will teach you what equipment is necessary and everything that must be considered from the moment you acquire it.

This last point is especially important because of the variation in percentages and the increase in oxygen, so you need to know what type of equipment is appropriate for each dive.

You will also learn all about oxygen exposure, from how it affects our body, to calculating partial pressures for specific depths according to the mix used, to what is the maximum partial pressure and depth to dive within safe limits.

You will even learn how to identify the correct labelling of nitrox charges, their use and recording. You will learn the basics of technical diving and all those important considerations to keep in mind when using mixtures with 40% to 60% oxygen.

Finally, you will master nitrox dive planning, either using a computer or tables (although the use of tables is not a widely used technique nowadays).

We hope that our guide has given you a better understanding of the role of nitrox in diving.

Always remember that this type of dives must be done with previous training and with the guidance of an expert in order to enjoy the experience with maximum safety.

If you have any questions or want to share your experience with us, the comment box is all yours!

You can also contact us directly if you would like personalised advice or if you want to venture into nitrox diving right away.

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