Nitrox a Quick and Easy Guide

Nitrox Diving: A Quick and Easy Guide
With proper training, enriched air scuba diving offers a wide range of advantages.

is how to use nitrox.

Nitrox, also known as enhanced air, oxygen-enriched air, EAN, EANx, or simply “nitrox,” is commonly seen on today’s dive boats. If you look closely, you’ll see the familiar green and yellow tanks that indicate the presence of nitrox divers. Recreational divers have been using it for decades, and every major training organisation offers a course in scuba diving with enriched air as a certification option.

Nitrox is a tool that can be effective when used correctly, but it can also be deadly if not utilised correctly. Increasing your no-stop dive time allows you to go deeper or surface more frequently, depending on how much gas is available. The problem is that it has a reduced depth restriction and other issues that you don’t have with air in recreational diving conditions.

What Is Nitrox?

A nitrogen/oxygen gas mixture with more than the usual air’s 21% oxygen content is referred to as enhanced air nitrox (EANx) in recreational diving. If you’re familiar with nitrox 32 (or 36), you’ll know it as either nitrox 32 (or 36) or EAN32 (or 36). (or 36). With this tank band, tanks loaded with EAN may be easily distinguished from air cylinders by their yellow and green colour scheme at the top, right below the crown. On a label or tag, you’ll find the oxygen mix percentage, which is critical because it impacts your maximum depth and no-stop dive time limitations.

How Is EAN Nitrox Created?

Enriched air has more oxygen than regular air, which lowers the nitrogen content. When utilising nitrox instead of ordinary air, you breath less nitrogen during the dive.

In our Open Water Diver training, we learnt that when you dive, the water pressure forces nitrogen from the air you’re inhaling to dissolve in your blood and tissues. The more nitrogen dissolves in the water, the deeper the dive and the longer the time spent at depth. It’s possible to develop decompression sickness if you emerge from the water with an excess of dissolved nitrogen in your tissues (DCS). In order to ascend to the surface without stopping, you must adhere to the no-stop limitations, which reduce the potential amount of dissolved nitrogen (but make your safety stop). In order to minimise the danger of DCS, divers who go deeper than the recommended maximum depth (such as techs and commercials) must decompress in phases as they ascend. On the Recreational Dive Planner, for example, the no-decompression time for a diver at 100 feet is 20 minutes. At a depth of 60 metres, a diver can expect a maximum stay of 55 minutes. Nitrox, on the other hand, alters these figures.

If all else is equal, you’ll have a longer no-decompression limit because you’re inhaling less nitrogen. Equivalent Air Depth (EAD) can be used to calculate this. This is the shallower depth that would allow for the same rate of nitrogen solution as air. To put it another way, at 105 feet, using EANx32, you’re absorbing nitrogen as if you were 15 feet shallower than you really are. A 66 percent increase in bottom duration means that the standard 15-minute no-decompression limit is extended to 25 minutes.

Benefits of Nitrox Diving

Nitrox is most effective when used at a depth of 50 to 100 feet. For shallow dives, no stop times are typically so long that you’ll run out of dive time before you’ve even emptied your tank. Assuming you’re using EANx36 at 60 feet, you’ll have a no-stop limit of 80-90 minutes for your first dive, therefore you’ll be limited by your gas supply, not your decompression restriction.

You’ve been taught to dive conservatively, but by pushing the limits outward, you may extend your dive time without compromising your safety. Divers often love pushing the envelope of their comfort zone with nitrox diving, even when they aren’t even close to their true no-stop limit. In the same way that air doesn’t ensure 100% safety, the chance of developing DCS can be reduced by remaining under acceptable ranges for the vast majority of divers.

Nitrox Scuba Diving: The Dangers

There is a price to pay for this benefit. High amounts of oxygen can be harmful, despite the fact that it is beneficial and necessary for life. As a result of oxygen toxicity, diving can cause convulsions or seizures as well as visual distortions, ringing ears, nausea and dizziness. Convulsions or seizures are the most dangerous while diving. Divers seldom experience oxygen toxicity, but if they do, it is often without warning and can result in drowning if the diver loses their regulator while convulsing. It is possible to become toxic with any amount of oxygen, but you would have to dive well below the stated depth limitations in order to do so with air. While recreational divers can go deeper with nitrox, the limit is set at the depth at which PPO2 reaches 1.4 ata, which is shallower with higher concentrations of oxygen. A different kind of oxygen exposure can be caused by prolonged exposure to high levels of oxygen. A nitrox certification is necessary because, among other things, divers using EANx must learn how to control their oxygen levels presently.

How to figure out your PPO2

There were no EANx dive computers or tables when enriched air was originally introduced into recreational diving. So, you used a pencil and a calculator to figure out everything.

If you’re afraid of math, don’t give up! Recreational nitrox divers no longer perform this manoeuvre. Your computer analyses your oxygen exposure and adjusts your no-stop duration when you input the maximum depth and the EANx mix you’re using. Actually, you’ll almost always finish the dive because you’re running low on gas, you’re cold, hungry, or you just can’t wait any longer to go pee. An enriched air (nitrox) course covers all of these topics and more, including how to analyse your mix and what equipment to bring.

If you don’t know what your computer is doing, you won’t be able to use the information it provides you in an accurate or safe manner.

Partial pressures, for example, are used to compute the pressure component of the oxygen limit. If you know the EANx oxygen % and the absolute pressure, you can calculate it (in atmospheres or bar). For example, a diver breathing air (21 percent O2) at 132 feet (5 ata) is breathing a partial pressure of oxygen (PPO2) of 1.05 percent. Breathing 105 percent oxygen at the surface would be a close approximation. In other words, even with pure oxygen, you can’t inhale PPO2 at the surface.

Calculating PPO2 looks like this if you’re curious: PPO2 is calculated as follows: 5 ata x 0.21 percentage O2 = 1.05 PPO2.

• Dropping the decimal point makes it simple to calculate the surface equivalent percent.

In order to compute the depth limit, we use the depth at which a mix would reach a PPO2 of 1.4: Max Depth = *(1.4 mix percent) – 1) X 33 Max Height

a decimal point is used to enter the mix percentage (e.g. 32 percent use .32)

A word of caution, however: Technical divers are educated in risk management techniques that allow them to safely dive to partial pressures of oxygen as high as 1.6 PPO2.

There’s Nothing Nitrox Can’t Fix

Enriched air is sometimes referred to as a “miracle cure-all” for all diving problems, however, it is not. To dispel a few common misconceptions, let’s take a look at a few facts.

Using it reduces your risk of being narced, according to popular belief.

This makes sense. If narcosis is caused by nitrogen, and you’re breathing less of it, you should have less narcosis as a result. The problem is that the depth range where you begin to worry about narcosis (100 to 130 feet) is also where you must cease using nitrox due to the risk of oxygen toxicity. Oxygen is supposed to be as addictive as nitrogen, so you’re still one step up and one step back even if you don’t use it. According to Dr. Peter Bennett’s chapter on inert gas narcosis in The Physiology and Medicine of Diving, nitrox’s preventative usefulness is “extremely modest, so minimal that I think it should be dismissed.”

Myth No. 2: You’ll use less gas because of it.

Likewise, this appears to be logical. You may not need to take another breath as frequently if you have more oxygen in each breath. Because most of the oxygen you inhale is expelled unused, it doesn’t operate that way. As long as you’ve got enough gas in your tank, your next breath won’t be affected by it.

One of the most common myths about nitrox is that it makes diving easier.

To put it another way, if you don’t have to do as much work off-gassing nitrogen, you should feel less fatigued. According to Bennett, many nitrox divers believe it, but a blinded investigation proves otherwise. Nitrox and air were administered to separate groups of divers, and both groups were asked how they felt afterwards. Bennett claims there was “no change.” People say, “It’s all in their heads.”

Myth 4: Enriched air allows you to go deeper underwater.

Those green-and-yellow cylinders have a “techie” vibe to them, which some divers equate with going deep. With EANx, there is a reduced depth floor, but the penalty for going below it (perhaps dying) is as severe. With regular air, many of us would risk going down to 150 feet, but with nitrox, we wouldn’t ever think about it. Decompression in the shallows after a deep dive may be one reason why some people think EANx is a deep diving gas, but tec divers use it.

Choosing the Correct Nitrogen Blend

Enriched air canisters are available in a wide range of oxygen concentrations, however, most retailers stock a predetermined blend.

The 32 or 36 percent pre-mixes given by most dive shops make things easy. It’s as simple as picking up the tank, looking at the mixture, and verifying the maximum depth in your computer.

There are different mixtures you can use. As long as the recreational maximum of 40% is not exceeded, your dive shop is likely to blend a tank to your specifications. You get the most bang for your buck with these custom mixes. On the other hand, the table NDL of 55 minutes is achieved by diving at 70ft with the EANx32 and the table limit of 45ft with the EANx40. This gives you more dive time for your money. Dive shops typically stock a specific EANx blend in locations where it is particularly beneficial due to the depth.

Safe use of Nitrox and other recreational gear

Standard dive equipment can be utilised at oxygen concentrations up to 40%, according to the U.S. Navy and the National Oceanic and Atmospheric Administration (NOAA). For recreational nitrox divers, there has never been a gear-related mishap because this is also the maximum limit for nitrox use. However, it is worth noting that other manufacturers have adopted a more conservative approach. When using a piece of equipment, make sure to follow the manufacturer’s instructions.)

Oxygen does not burn, as is commonly believed.

A high concentration of oxygen, however, greatly increases the flammability of anything it comes into touch with. The scuba tank is the one piece of equipment that is an exception to this rule for two primary reasons.

To begin with, manufacturing nitrox entails injecting pure oxygen into a tank, followed by a second layer of air that is specifically filtered for oxygen compatibility. Because the tank contains pure oxygen during blending, the components (o-rings, valve seats, and any lubricants) and any lubricants must fulfil oxygen service standards. A particular cleaning of the tank is also required, which is carried out once a year.

The second reason is that the tank must be prominently labelled to prevent it from being mistaken for air, as you discovered. Even when surrounded by a swarm of cylinders, the characteristic EANx band at the cylinder’s apex is easy to spot.

Become a Certified Nitrox Diver.

E-learning for enriched air courses is available, and it may be completed in just a few hours. In-person training takes a couple of days and provides you with the opportunity to work with a dive professional to assess a tank, adjust your dive computer for nitrox, and complete an enriched air record.

Definitions and Formulas for Nitrox

• Normoxic nitrox: Air that has been cleansed and has had the oxygen content increased to 21%

Air with more than 21% oxygen is known as “enriched air” or “enriched air nitrox.”

Ead, or Equivalent Air Depth. Nitrogen is absorbed at a specific depth while breathing nitrox compared to the depth at which a comparable rate of absorption would occur while inhaling air.

Percentage of oxygen in the atmosphere x PPO2 = PPO2 (or PO2).

• MOD or maximum depth: Max depth = *(1.4 ÷ mix%) – 1) X 33

1.4 ((Depth + 33) 33) 33) = best mix