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23.06.2020
Egypt, South Sinai Governorate, Dahab
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What is the NITROX thing, and is it for me?

  • Open Water Diver
  • Advanced Open Water Diver
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Dahab Days Diving Center

In the Oxford English Dictionary Enriched Air Nitrox (EANx – where x is the percentage of oxygen) is defined as “a mixture of oxygen and nitrogen used as a breathing gas by divers, especially a mixture containing a lower proportion of nitrogen than is normally present in the air, to reduce the risk of decompression sickness.” As scuba divers we focus on the oxygen content, even though the main benefits of nitrox are derived by the lower partial pressure of nitrogen.

The reason for this is that oxygen becomes toxic at depth. Since the nitrox blends we use in scuba have an increased percentage of oxygen, the maximum operational depth – or MOD - of the gas is important. The higher the percentage of oxygen in the blend, the shallower the MOD. There is a balance between the percentage of oxygen (oxygen toxicity and desired depth) and extended dive time (reduced nitrogen exposure) which we exploit to determine the optimal gas mix to use on our planned dives.

I have heard a number of myths about diving on nitrox, and in most cases they are exactly that; myths. Let’s take a look at the most common ones.

Myth #1 – Nitrox is for deep diving.

Some divers think that EANx is for deep diving, when it’s not. The myth that nitrox lets you dive deeper is a dangerous misconception. nitrox has an increased oxygen percentage. As the amount of oxygen in the mix increases your diving depth (MOD) decreases. It does not increase. You must be sure to get the necessary training and gain the appropriate certification before you use nitrox on a dive.

Myth #2 – nitrox reduces your air consumption.

Whilst nitrox will extend your no decompression limit, it’s not true that it will reduce your air consumption or somehow (through magical means) make your air last longer. Your air consumption when scuba diving depends on several factors. These include the conditions, depth of your dive, your buoyancy, streamlining, your technique, work rate, and your level of fitness. None of the above factors have anything to do with the percentage of oxygen contained in your tank. Your gas consumption will be the same regardless.

Myth #3 – Diving on nitrox is safer than diving on air.

Many people say that diving on nitrox is safer than diving on air. You could argue that there’s some truth to this, as you don’t build up the same levels of nitrogen in your body when diving on EANx. This may reduce the risk of DCS. Safety is more about your approach to diving. Diving on nitrox requires you to follow the same strict safety rules and procedures as you would if you were diving on air. If you’re diving on nitrox, things can still go wrong, and if you don’t follow safe diving practices, you are just as likely to get into trouble.

Myth #4 – You’re less tired when you dive on nitrox.

Diving on nitrox and being less tired is a “half-truth”. As nitrogen builds up as we dive, we can end up with a lot of residual nitrogen in our system. This may be particularly true when diving to excess on a liveaboard. As nitrogen accumulates in your body tissues, it can cause you to feel weary. It follows that taking less nitrogen on board should reduce that feeling. However, as most information around this is anecdotal it is difficult to prove.


Now we have dispelled the myths around the “magic gas” let’s look at the pros and cons of using nitrox.

Pros

1. Increase your dive time at specific depths as using nitrox significantly extends the No Decompression Limit (NDL). If you use a 36% mix at 24 metres, you double your bottom time from 30 to 60 minutes.

2. Shorter surface intervals. As a nitrox diver you will have less nitrogen to “off-gas” than when using air, which shortens your required surface interval.

3. Longer repetitive dive times. Using nitrox you have a longer bottom time than using air on your subsequent dives because you absorbed less nitrogen on your previous dives.

4. Risk mitigation: add a buffer zone. Many divers choose to use nitrox whilst following an air profile adding a significant buffer to their no-decompression limit and reducing the risk of narcosis and potential DCS.

5. Less fatigue. There is a significant amount of anecdotal evidence that using nitrox may reduce post-dive fatigue, ensuring you don’t fall asleep and miss the next dive!


Cons

1. It’s more expensive. A nitrox fill usually costs around 50% more than air. However, a lot of places offer free nitrox or have bundled offers making nitrox diving a great option. Most centres have their own analysers that you can use so you don’t have to buy one. Although having your own is a good idea – especially on day boats and liveaboards- as you cannot always analyse beforehand.

2. The higher the percentage of oxygen, the shallower you can dive. For most recreational diving blends of EAN32 and EAN36 are suitable with MODs of 33.75m and 28.88m respectively at ppO2 of 1.4. These mixes are usually available at most locations.

3. If your diving buddy doesn’t use nitrox when they’re diving, you’ll need to dive using an air profile. You will lose some of the benefits of nitrox. This does make for a safer, and possibly shallower, dive as we explained earlier.

4. Nitrox is not always available where you dive. Check before you book your liveaboard or resort trip.

If you want to become an Enriched Air Diver, we have a very special offer that might interest you! Please contact us at info@dahabdays.com or by phone/WhatsApp on +20 100 051 5039 and one of our team will help you.

Dahab Days Diving Center
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