Scuba diving is a thrilling hobby allowing one to chart the underwater world that lies just offshore. It’s exciting to dive into the unknown and see things hidden just below the waves. It’s so captivating you might want to stay underwater as long as possible, but the limits are strict. You may remember from your Open Water course that as a diver, you are always limited by so-called no decompression limits. In other words, the nitrogen in our bodies limits us from staying down too long. But what if we reduced the amount of nitrogen we breathe?
Nitrox is a mixture of enriched air, a carefully calculated arrangement of gasses which we breathe every day. Enriched air Nitrox, or EANx, is known as a mixture with more oxygen than the standard above-water air. Anything with more than 21 percent oxygen is “enriched”. Tanks with this mixture are clearly marked by the percentage and by a green or yellow band on them.
Nitrox is great for scuba diving, but it’s not the same as normal air. In order to use Nitrox on a dive, a certification is required. The certificate is given at the end of a personal or public training course where users are taught the correct way to use scuba gear and the safe way to breathe it when going down or returning to the surface. For those who have an Open Water certification already, obtaining a Nitrox Certification can unlock the next step of adventure you are looking for!
Also check out our article on Air vs. Nitrox!
What specifically is different between Nitrox and air? What is the difference between a scuba-safe air cylinder filled with regular compressed air compared to Nitrox? The primary difference is in the mixture of oxygen which replaces the present nitrogen. The regular air we breathe daily is 78% nitrogen and 21% oxygen with about 1% left over for other latent gasses like carbon dioxide, neon, hydrogen.
The lower amount of nitrogen is what makes Nitrox air different. When under pressure, nitrogen compresses – it becomes smaller – inside the body. This is due to Henry’s Law, which states that “the solubility of a gas in a liquid is proportional to the partial pressure of the gas over the liquid”. As we go back up to the surface, the nitrogen expands and leaves the body – we are in the decompression stage.
Our bodies, however, can only tolerate this happening at a certain speed. If we stay down too long and load up too much nitrogen, and then resurface too quickly, the nitrogen comes out too quickly, forming bubbles in our bloodstreams. This leads to a dangerous situation, known as decompression sickness or “The Bends”.
You can imagine this like a can of Coke. If you shake it and increase the pressure, and then open it all too sudden, it will foam over. The same happens to your body if you resurface with too much residual nitrogen in your cells. To prevent that we ever get into this situation, we have No Decompression Limits (NDLs), which dictate how long you can stay at which depth and still resurface safely, that is, without having to complete decompression stops on the way up.
For instance, the NDL for 100 feet / 30 meters is 20 minutes based on the Recreational Dive Planner table. If you want to stay longer, you either have to complete decompression stops on the way up – but this requires technical diving and advanced training. The much easier way: you can reduce the amount of nitrogen you load into your cells by using Nitrox!
Another drawback of nitrogen is Nitrogen Narcosis. As you descend into the depths, your body gets more susceptible to the so-called “narc” or “narcosis”. This usually happens at depths below 100 feet and can lead to blurred tunnel vision and feelings of drunkenness. With less nitrogen mixed into the air, Nitrox helps to prevent these incidents altogether. The main purpose of Nitrox is to extend the bottom line time, or the No Decompression Limit (NDL). This is the period where a diver has been underwater and under pressure to their body’s natural limit.
Certification is done through an accredited Nitrox course hosted or run by professional diving instructors. This can be done in person at a diving school, a diving shop or through online Nitrox certification.
There are three primary organizations that handle scuba training and Nitrox certification. Those groups are the Professional Association of Diving Instructors (PADI), the Scuba Schools International (SSI) and Scuba Diving International (SDI). These are arguably the biggest organizations represented in most diving shops.
There are further organizations that offer Nitrox diving, but these are the most prominent ones out there. Getting a Nitrox certification from any reputable provider is an absolute must before using Nitrox on your dives. That said, any of the accredited organizations have all the expertise and professional skill required to offer courses that will teach you how to safely dive with Nitrox.
In principle, it is easiest to stick to the organization you have done your Open Water certification with. However, that is not mandatory, as a crossover is possible anytime.
PADI offers an online Nitrox course with various payment structures available. These are good for divers who already have some experience and want to try something new. The Nitrox or enriched air course teaches how to dive with Nitrox, using an oxygen air analyzer and setting a dive computer. A certificate from a PADI approved Nitrox course allows you to get Nitrox air fills at diving shops.
In theory, Nitrox certification does not require any in-the-water training. However, it is strongly recommended to do at least one dive with an instructor, including analyzing the tanks and preparing the dive before. The online course can take between 2 and 4 hours, while the practical experience at a dive shop with an instructor can take one to two days depending on the availability.
Criteria: 2-4 hours Online Course and Exam
SSI has an online Nitrox course which offers two different grades of certification, one for 32% and one for 40%. These are the mixtures of Oxygen in Nitrox. The Nitrox courses also teach practical skills to safely plan and dive with enriched air mixtures, such as calibrating an oxygen analyzer, how to check and analyze nitrogen cylinders and other necessary safety checks.
The Nitrox Course costs $175 as a single one-time payment. This will handle the online Nitrox certification through a self-learning setup of educational material with practical exams. Students who sign up for the 40% Nitrox course will be required to complete a face-to-face examination, however these may be done online as well using facetime apps like Zoom. In order to qualify for the Nitrox course, proof of Open Water Diving is required in the form of a separate certificate. The minimum age for this program is 10, and it is geared towards applicants of all ages.
Criteria: 6-10 hours all online
SDI certification is among the cheapest available. Like the other organizations, SDI offers the course in many different languages for international learners. Study materials are also provided through the course. The Nitrox course covers the physiology of breathing Nitrox gas mixtures, how to safely use up to a 40% oxygen enriched mixture as well as the ups and downs of Nitrox diving.
The Nitrox course costs $144.15 for the online Nitrox certification only. Also required are pool or open water training. Open water diving training is required, but a student can be enrolled in both courses simultaneously to further their understanding of diving safety concurrently. In order to pass, a 100% comprehension of questions and answers is required throughout the Nitrox course. Students must analyze at least two Nitrox cylinders for errors, log at least one and learn how to program a Nitrox computer correctly.
Criteria: Approximate One Day, required face-to-face online or offline
All three groups are recognized as the highest professional grading when it comes to certification. A certificate from any one group is good for any diving shop to approve the loaning of Nitrox diving equipment. Other clubs or programs may offer certification of their own. Additionally, not all of these organizations operate in all countries. Make sure your certification is valid for the areas you wish to dive in. PADI has the largest coverage. It is best to check if their certification can match the same credentials as a more widely recognized group.
Overall, each group has different courses, they all teach the same essentials about diving with Nitrox. There is no reason to stick to only one organization, or to pursue certification from all three. Pick whichever is most convenient for you, or which is offered at your local diving shop. Achieving proper open water diving credentials with any one will allow you to access their Nitrox course as well.
With courses out of the way and a certificate in hand, how much does it cost to go for an afternoon of well educated, practiced and practical Nitrox diving? Costs can differ based on location and availability. Nitrox as a substance is not always available. It requires gas blending, which not all dive shops will offer.
Because the air is special and requires that specific mixture, it is more expensive to fill. The tank itself is specially marked so it is not confused with tanks holding regular air. Generally the cost for Nitrox is between $2 to $5 more expensive for a fill. It won’t break the bank at all. If you are prepared to go diving and want the longest bottom time per dive, you can consider taking on that small extra cost.
Is it worth the higher cost to use Nitrox when diving? It can be. Dives are set by a time limit that is partially determined by the air you have and the body’s NDL. However, with Nitrox, you will be able to stay submerged for longer than you would otherwise on air. Nitrox helps extend the NDL for more time underwater.
This is possible due to the lowered nitrogen percentage in enriched air, which leads to less overall nitrogen absorption. Nitrox reduces the risk of decompression sickness. Less nitrogen in the body means surface intervals can be reduced between dives to rest the body, and it lowers the risk of repetitive diving. If you plan to go diving from a liveaboard many times in a single day, Nitrox makes that easier.
As long as divers stay within the natural limits they are educated on, they can sustain long dives without fear of decompression sickness. It gives you more thrill, more time under the water to interact with and observe the majestic marine scenes around you without needing to keep one eye on a running clock, or needing to worry about your vision giving out as your body is taxed too hard.
Nitrox is not a perfect solution. Compression and decompression have huge effects both immediate and long lasting. While Nitrox can help against some of those effects, it cannot help against all of them. Some of the positive effects such as alleviating exhaustion or fighting fatigue lack consistent scientific reporting.
One of the key issues in scuba diving is oxygen at pressure. Yes, we need oxygen to live, but our bodies are programmed and trained to only need so much of it. Learning how to manage oxygen exposure is one of the key components of any online Nitrox certification course. One of the essential factors is learning to calculate PPO2, or Partial Pressure of Oxygen. A safe PPO2 is 1.4 when active and 1.6 when resting. You expose yourself to risks if you go to or stay at the wrong depth.
The maximum operating depth, or MOD, for Nitrox depends on the air mixture. Everyone in a group has to have the same mixture to stay at the same depth. Divers who are trained and comfortable with solo diving can use Nitrox more freely than divers who go in groups. Even though it is not much more expensive than compressed air, it still has a limit to its availability. When the Nitrox refills run out, the benefits it carries end.
Nitrox may sound like a miracle for diving, but it is just another option for a unique kind of diving. It is not a method to achieve perfect diving all the time. There are some things you might have heard about, myths about how Nitrox makes everything better, but here are some truths to keep you safe.
1. Nitrox Prevents Narcosis
Breathing nitrogen at depth can cause narcosis, so if there is less nitrogen in the air you breathe, it won’t happen, right? That is not true. In fact, the same thing can happen with oxygen. Narcosis primarily happens at depth and Nitrox does not allow for especially deep diving, normally out of the MOD Nitrox supports. Some people get it and others don’t, but the early symptoms are resolvable with a careful ascent of a few meters.
2. Nitrox Reduces Gas Consumption
If there’s more oxygen in each breath you take, you don’t need to breathe as much to get the same lungful that you need. That is not right. The volume breathed is unchanged in any meaningful way. Even with the natural air we breathe, a portion of oxygen is exhaled even on the deepest breaths held for the longest time.
3. Nitrox Relieves Fatigue
Again with oxygen, we experience fatigue when we don’t have enough of it and can’t supply it to our body fast enough. So more oxygen means less fatigue. That’s not quite true. Your body can definitely feel the hit of extra oxygen, which can provide a cover-up placebo effect, similar to how athletes use canned air to breathe deep between big plays. It does not improve health, it just makes you feel better.
4. Nitrox lets you Dive Deeper
The opposite is true. Nitrox does not allow deeper dives, it is for lengthening the NDL on dives to stay down longer. Depending on the gas ratio, Nitrox will restrict you to shallower depths. The general limit for Nitrox diving is between 50 and 100 feet or slightly deeper, depending on the mixture. Nitrox is mostly to alleviate decompression symptoms. It’s for coming out of the water faster and easier. It’s actually easier to go deeper with regular air in a safe and controlled manner.
Nitrox can make your scuba diving experience much better, but only if you know how to properly use it. Getting a Nitrox certification is essential. Most diving shops will not allow you to try it if you haven’t learned how. Nitrox lets you stay in the water longer to see more amazing sights, it lets you come out of the water faster while subduing any health risks, and it puts you a step closer to the undersea life that most people can never see beyond the surface.