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What is Nitrox or Enriched Air?


Nitrox diving has become increasingly popular amongst scuba divers over the last few years. It’s no longer a surprise to see green and yellow tanks of Nitrox or oxygen-enriched air in dive shops and on dive boats all around the world. Even though it’s becoming more common, it is not the standard. The reason nitrox isn?t more widely accepted is due to a reputation problem, it is often confused with jargon related to technical diving. But it has been used in recreational diving for over 25 years.


If you don’t really know what diving with Nitrox really means for you, and you are wondering whether or not you should try diving with it, we’ve put together a practical guide that will tell you what you need to know about Nitrox diving. Including what Nitrox is, what Nitrox is for and the risks that come with using enriched air.


What is Nitrox exactly, and what does it do?


When you’re talking about Nitrox in general, it is simply a mix of nitrogen and oxygen. In diving terminology, however, it is a special gas mixture of nitrogen and oxygen, with the oxygen concentration higher than the normal 21% found in the air we breathe.


These mixtures with more than 21% oxygen are used in recreational and professional diving. There are a few different names to describe these. The mixtures can be called Hyperoxic Nitrox, SafeAir, and/or Enriched Air Nitrox (EAN or EANx). Tanks with EAN are typically labelled with a Nitrox tank band on the outside, with the oxygen percentage in the mix (the ?x? in EANx being this percentage) written somewhere near the tank’s valve. For example, 40% oxygen in the mix would be labelled as EAN40. This gas mixture can come in a variety of ratios, but the most popular blends are the following:


  • Nitrox I Also known as Nitrox 32, Nitrogen 62/32, and EAN32, has 32% oxygen and 68% oxygen and is the most commonly used type.
  • Nitrox II Also known as Nitrox 36, Nitrogen 64/36, and EAN36, has 36% oxygen and 64% nitrogen.


How does Nitrox/EAN benefit divers?


Decompression sickness, also known as ‘the bends’ is something scuba divers want to avoid at all costs. This potentially deadly condition is the most serious risk of deep water diving. It starts when nitrogen from the air you breathe dissolves in your bloodstream as you dive deeper into the water and the pressure increases. If the nitrogen builds up too much and you resurface too quickly, without performing decompression stops (during which your body will take its time to expel the absorbed nitrogen), you may experience decompression sickness. In our blog about the surface interval, we elaborated more about decompression sickness, the symptoms and how to easily avoid it.


It’s important to note that this gas mixture doesn’t allow you to dive deeper than your regular air (79/21) tank. Since the increase in oxygen equates to a shallower maximum operating depth for your gas tank. Your regular Nitrox mix (Nitrox I and Nitrox II) is good for mid-deep dives ranging from 25-35 meters. It’s important to set your dive computer to the right mix and plan your dive accordingly.


Extending your bottom time.


An important part of any Open Water Diver Course discusses that the build-up of dissolved nitrogen in the tissues. When breathing Enriched Air, less nitrogen builds up during the dive, therefore, you can stay longer at depth whilst still remaining within your no stop recreational limits. You can compare a diver’s oxygen exposure with a burning candle. You can snuff out the wick with your fingertips without injury, but hold a finger in the flame for a few minutes and serious damage will result.


An example, if you are diving at 28 meters on 36 percent Nitrox, you will have a bottom time of 50 minutes (according to US NAVY dive tables, always follow your computer). If you were to compare this to a dive table for regular air you would have 30 minutes at 28 meters. While Enriched Air it does not eliminate the risk of decompression sickness or nitrogen narcosis, it lowers it significantly when spending prolonged time at depth.


Enriched Air is said to give you more energy after diving.


Many Nitrox divers claim that diving on enriched air leaves them feeling less fatigued than when they dive using regular air. While this theory has not been scientifically proven yet, we are more than happy to accept any kind of help to make diving even more enjoyable. Even though we love sleeping and relaxing on our spacious boats on the way back from an intensive day of diving, it’s a good feeling that you still have the energy to enjoy the stunning views in the Komodo National Park if you want to.


Shorter surface intervals when diving on Enriched Air.


While it doesn’t really affect us too much in the Komodo National Park (since we have to drive the boat to the next dive site, and we need some time to enjoy our delicious snacks), waiting for at least an hour to get back in the water after you just came up from a beautiful dive can be a bit of a bummer. When diving with Nitrox, your body is exposed to less nitrogen during your dive, so it will have less nitrogen to get rid of to allow you to get back in the water. Theoretically, this should greatly reduce your necessary surface interval time; however, please always refer to your dive computer or your enriched air dive tables for the most accurate way to track your needed surface interval time. Find out more on our blog about the Surface Interval


Nitrox gives you longer repetitive dives.


When visiting the Komodo National Park you want to make the most out of the days you have in the Park. Depending on whether you are diving on our day boat, or our liveaboard, you could be diving up to four times per day. That’s an impressive amount of diving. Which also means a lot of time off-gassing is required. If you’re diving on normal air, your time at depth is gonna get shorter and shorter as the day goes on.? But if you are using Nitrox, again, the nitrogen build-up will be reduced. The benefit to this is that those who are diving with Nitrox can continue diving at a greater depth for a longer time than someone diving on air.

Nitrox at Manta Rhei


The PADI Enriched Air Diver course is an interesting and valuable speciality scuba course, unlike other specialities, there is no learning curve and you can start enjoying the advantages right away. At Manta Rhei we offer this course on a daily basis and whenever it suits you. The best part about the course is that you don’t even have to get in the water to get certified. So you can do the course and enjoy diving the next day with a free upgrade to Nitrox.


During the course, you’ll learn how to safely dive enriched air Nitrox. Firstly, you will need to develop an understanding of what enriched air is and what additional risks are involved when you choose to dive with enriched air. Our team of instructors and divemasters are all Nitrox certified and are happy to chat with you through any questions you might have, this in combination with the theory book and the video we’ll provide you with will set you up for the exam. The examination on the material is to ensure you properly understand the benefits and risks of enriched air diving.

Safely diving enriched air also involves learning the theory behind Nitrox, and practical skills to make sure you are able to dive in a safe manner. This will ensure you are confident once you have earned your Enriched Air certification and start diving enriched air.

You’ll also learn how to properly mark your Nitrox cylinder to avoid confusing it with a bottle of air or another diver’s enriched air cylinder. In the practical part of the course, you will learn the proper procedure for obtaining enriched air including what documentation is required.

So in conclusion, as stated above there are a lot of benefits becoming an enriched air diver.

Nitrox will give you a longer bottom time due to less nitrogen build up in your tissues, it’ll reduce your surface intervals because there is less nitrogen absorbed in your system. Also, you can perform longer repetitive dives which are especially interesting if you are on a liveaboard.

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