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A Beginners Guide to Nitrox Diving

A Beginners Guide to Nitrox Diving

Written by Noreen
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Published on September 7, 2018

Nitrox diving has become very popular among scuba divers—so much that you can almost always spot green and yellow tanks of nitrox or oxygen-enriched air in dive shops and dive boats all around the world. Often confused for jargon related to technical diving, it has been widely used in recreational diving for over 25 years.

For anyone unfamiliar with nitrox and wondering whether or not they 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 it is, what it’s for, as well as the risks that come with using it.

What is Nitrox and Enriched Air Nitrox (EAN)?

two yellow and green nitrox tanks against textured beige wall
Image via Shutterstock

Nitrox is simply a mix of nitrogen and oxygen. In diving terminology, however, it is a special gas mixture of nitrogen and oxygen, but 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 sport diving and are alternatively called Hyperoxic Nitrox, SafeAir, and or Enriched Air Nitrox (EAN or EANx).

Tanks with EAN are typically labeled with a nitrox tank band on the outside, while its mix percentage (the ‘x’ in EANx being the percentage of oxygen) is written somewhere near the tank’s valve. For example, 40% oxygen in the mix would be labeled as EAN40.

This gas mixture can come in a variety of ratios, including less than 21%. 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.

With a higher amount of oxygen and lower amount of nitrogen, divers can lengthen their no-decompression limits, shorten surface intervals (or the time spent at the surface between dives), and achieve a greater buffer for decompression safety in certain diving conditions.

While diving with this gas mixture does sound impressive, especially for beginners, it really is just like any other piece of scuba diving equipment that you’ll need to understand and properly use in order to avoid any dangers and make the most out of. Let’s delve further into how nitrox works when we compare it with regular gas tank diving in the next section.

How does Nitrox/EAN benefit divers?

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As a scuba diver, you’ve probably already heard of decompression sickness. Also known as “the bends,” this potentially deadly condition is just one of the many major risks 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 also increases.

Once the nitrogen builds up 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. Symptoms include joint pain, dizziness, and extreme fatigue, and can result in mild numbness of the limbs, paralysis, and even death.

The benefit of using nitrox instead of regular gas is that it helps increase your allowed diving time as it offers less nitrogen (and more oxygen) for you to inhale, thus reducing the amount of nitrogen that will quickly dissolve into your body—thereby lengthening your no-decompression limit. While it does not eliminate the risk of decompression sickness or nitrogen narcosis, it lowers it significantly.

It’s also important to note that this gas mixture doesn’t necessarily allow you to dive deeper since the increase in oxygen equates to a shallower maximum operating depth for your gas tank. Your regular mix is good for mid-deep dives ranging from 20-40 meters (60-130 feet).

Nitrox Dive Table

Waterproof Dive Table

Fortunately for nitrox divers, today’s dive computers are able to provide all the necessary information—including bottom and surface interval times—according to several important factors such as your depth and nitrox content. But when your dive computer fails, it can be life-saving to have a backup plan. This is where dive tables come in.

Dive tables such as the NITROX 32% Waterproof Dive Table above are easy to follow for both single and repetitive dives. They are typically made of waterproof plastic so you can bring them with you for easy reference underwater. They also offer imperial and/or metric calculations based on the standards set by the National Oceanic and Atmospheric Administration (NOAA). Dive tables can be as small as the one above (7” x 9”) and easily stored in your emergency dive kit or attached to your body with a lanyard.

Risks of Nitrox Diving

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While nitrox diving can contribute to longer bottom times during no decompression dives while reducing the risk of nitrogen narcosis, it comes with its own concerns.
While we definitely need it to live, too much oxygen exposure can also be harmful to the body. Referred to as oxygen toxicity, high concentrations of oxygen can lead to seizures, unconsciousness, difficulty in breathing, lung damage, eye damage, and even death. Another scary thing about oxygen toxicity is that you may get little to no warning before you start seizing, and this can lead to near-certain death by drowning.

As nitrox contains a larger percentage of the highly flammable oxygen, its tanks and valves must also be handled properly and cleaned with care to avoid unintended explosions.

The bottom line is, nitrox diving is not any less dangerous than diving with regular gas. Nonetheless, it should be done right. With the proper training (Nitrox Certification) and proper adherence to guidelines, risks can be decreased and divers can enjoy a whole new level of scuba diving.