Why you should consider becoming NITROX qualified
Nitrox or more precise Enriched Air Nitrox EAN has been available to recreational divers for over two decades but is still not well understood by many divers.
Enriched Air Nitrox is created by adding additional oxygen to the compressed air filling your scuba tank. The air that surrounds us is approximately 78% nitrogen and 21% oxygen. By adding oxygen we change that ratio. In scuba diving, we identify the percentage of oxygen in our cylinders. If the cylinder has 32% oxygen we refer to it as EAN32.
Rewards
That raises the question, what good does that do you? Honestly, the extra oxygen does little for you. It is the decrease in nitrogen that is the key to the success of EAN. Using EAN either:• Extends your bottom time for a specific depth or
• Decreases your risk for a specific depth.
As you know, when we dive the increase in pressure impacts on the amount of gases in our bloodstream and in our tissues. More nitrogen enters our bodies. As we return to the surface that nitrogen needs to leave our body. Having too much nitrogen in our system can cause decompression illness. Scientific studies have determined how long we can stay at a certain depth and ascend directly to the surface with the nitrogen level in our system still at an acceptable level. This is the No Decompression Limit or NDL. If we go beyond our NDL, then we must make decompression stops on the way to the surface.
The benefit of using EAN
The benefit of using EAN at depths is that there is less nitrogen available to be forced into our tissues that has to be removed, to surface safely. Let’s look at some examples.
Imagine a great dive to 25m using standard air. At around 29 minutes you would reach your NDL. If you used EAN32 (32% oxygen) we can stay for 37 minutes, which allows over 20% more bottom time. If I use EAN38 (38% oxygen), my NDL extends to 56 minutes. In this example using EAN38 and possibly also with EAN32, we shift our limiting factor. But many divers will use Nitrox while maintaining their air NDL, or set their computers for air to create larger margin of safety.
You will often hear people say that with Nitrox you can go deeper. That is not 100% true. In fact it could be 100% deadly. Using air at 25m our NDL is 29 minutes.
However, using EAN32 we can dive to 33m before needing a 29 minute NDL. So it could be that you can dive deeper if you are just comparing depth and a set NDL. But there is a limit.
The risks of EAN
A thing that irritates me when I read a news article about scuba diving is when a reporter calls our scuba tanks oxygen tanks. Except for very limited use in technical diving, and as a first aid measure on the surface, we do not use pure oxygen. The very simple reason is that it can kill us.
At a high partial pressure oxygen (ppO2) can become toxic causing our bodies to go into convulsions and shutting down our organs. Each of our body’s will react differently but having a ppO2 of 2.0 is considered lethal. Recreational divers are trained never to exceed a ppO2 of 1.6 and to plan their dives using a ppO2 of 1.4. The NDL times used in the examples above used the 1.4 limit.
When we plan our dive with air we concern ourselves with nitrogen intake expressed as NDL and how long the air will last. The ppO2 does not come into play because we will not reach the 1.4 ppO2 until we are past 56m. Our NDL and air supply will not let us go that deep with a single tank, and return safely to the surface.
However, if we were to go on a deep dive to 40m, the limit of recreational diving, air would give us 9 minutes and for most divers the NDL would be the controlling factor of the dive. Using EAN38 at that depth would give us a 1.90 ppO2, well outside the safety limit for recreational divers and possibly lethal. Even using EAN32 would put us above the planning limit and at the edge of the safety limit. These issues require training.
Oxygen content of every EAN cylinder must be verified
EAN divers are responsible for verifying the oxygen content of their cylinder before each dive.
Cylinders containing Nitrox must be marked. Using a gauge, they check the oxygen content, calculate their Maximum Operating Depth or MOD, and record both on a log. They also mark a sticker on the tank with the MOD and oxygen percentage. The MOD tells the diver how deep they can go before reaching the 1.40 ppO 2 limit.
Get trained as Nitrox diver
Nitrox has no benefit to offset the additional cost if you are diving at 10m or shallower. The air supply will give out long before the NDL time is reached. Beyond that depth a shift occurs where the NDL becomes the controlling factor. When you can choose to increase your dive time you get more options.
The training course to be certified to use EAN is short. The theory segment explains the descriptions above in more detail, and shows you how to analyse your gas supply. It requires just two open water dives. Many dive schools will combine open water training or advanced open water training with an EAN diver course requiring just one extra dive.
One more thing. Many divers report feeling fresher after diving with Nitrox but scientific studies have provided no evidence Nitrox boosts your energy levels or reduces fatigue.
