Enriched Air Nitrox
What is Nitrox
It isn’t long after you’ve learned to dive that you start hearing more and more about Nitrox/Enriched Air Nitrox. You may have a notion of what it is but do you really understand what makes it so popular?
If you have any questions we’ll try to address those here.
Firstly, let me get right in there and say: the contents of this blog are to provide extra information and a greater understanding; but does not constitute nor replace the need for proper training from a qualified professional prior to using Nitrox.
Nitrox is simply a word used to describe a gas mix comprised of Oxygen and Nitrogen. Air is comprised of these two gasses; therefore air is Nitrox (+/- 21% Oxygen, 79% Nitrogen). In the context of recreational diving we talk about ‘Enriched Air’ or ‘Enriched Air Nitrox’ (EANx). This means air which has been enriched with additional Oxygen, up to a maximum concentration of 40%
The primary reason for this is simple: to extend our no-decompression limit.
How does that work?
Our no-decompression limit is the time limit that we can spend at depth without requiring special procedures to return safely to the surface. As long as we remain within our no-decompression limit then we can end the dive by simply ascending directly to the surface, albeit at a slow and steady pace.
If we stay beyond our no-decompression limit then we are now making a ‘decompression’ dive, and will need to make staged decompression stops on the way back to the surface to allow our bodies to off-gas.
The reason for this is that while diving, we are breathing our gas at a higher pressure than normal. The Nitrogen which comprises the majority of our gas is inert (meaning it does nothing for us) and so our bodies will simply begin absorbing that gas.
The deeper we dive and the longer we spend at depth the greater the quantity of Nitrogen we will absorb. We can tolerate a certain exposure without the need for employing the special procedures mentioned above. This controlled, limited exposure is what we call the ‘no-decompression limit’.
So how does Nitrox help?
By enriching our air with additional Oxygen, we are therefore removing a portion of the Nitrogen. By breathing less Nitrogen, we absorb less. This means that we extend our no-decompression limit beyond that which we are obliged to observe while breathing air.
So is Nitrox better for deep dives?
Well, yes and no.
It is true that on shallow dives our no-decompression limit is usually longer than our tank would last us, so arguably the benefit of breathing Nitrox on a shallow dive is moot. At 30 metres, however, the different gas mix could easily provide us with as much as 50% extra bottom time, which certainly isn’t to be scoffed at.
There is a limit to the safe range we can use the gas, however. We all know that we can have too much of a good thing; and Oxygen is no exception. Prolonged exposure to elevated pressures of Oxygen can result in the diver experiencing Oxygen toxicity – something which can prove to be fatal underwater.
To address this risk, the recreational diving community sets very conservative limits to our exposure to oxygen. (This is also the main reason why formal, thorough training from a knowledgeable dive professional is so important!)
One of the limits imposed on us while using Nitrox is maximum depth which we can safely breath the gas. This is why Nitrox is great for deep dives, but only up to a point! The most popular Nitrox blend still allows the diver to go safely to just beyond 30 metres whilst still providing ample additional bottom time: which is a pretty ideal range for recreational divers.
What else is it good for?
We’ve already addressed the primary benefit of Nitrox, and touched on the main draw-back; but that’s not quite the full story…
Nitrox is a great gas to breathe if you are going to be diving intensively, even if the depths are not going to be extreme. If you go on a liveaboard diving trip, for example, then you may make 4 or even 5 dives a day. Nitrogen takes several hours to be fully eliminated from your body after a dive, and a heavy-diving schedule means that you’ll constantly be topping up your residual Nitrogen levels. Over time you’ll notice your no-decompression limits becoming more and more restrictive.
Enriched Air Nitrox will help with that.
Another significant benefit to Nitrox is to factor in extra inherent safety and conservatism to your dive profile.
As we age and become less fit, our bodies take longer to fully eliminate the excess Nitrogen and we become more prone to Decompression sickness, even staying within accepted ‘safe’ limits. Many divers opt to breathe Nitrox on their dives, but observe the no-decompression limits of air. This is a fantastic way to build in a safety cushion for this who feel that they aren’t as fit as they once were.
When is the right time to learn about Nitrox?
Well, frankly, it is never too soon. Many divers learn about Nitrox whilst completing their entry-level diver training – and why not? It is not a mystical thing, and it does not require any specific additional skill or experience in order to begin benefitting from it. The right time to do the course depends on how much you dive!
If you only ever do one day of diving, once a year during your summer holidays; then there really isn’t a significant benefit to you to learn just yet. You may still chose to, simply for your own knowledge development and sense of accomplishment. That’s up to you.
It usually isn’t long before divers ‘get the bug’ and decide that these few dives just aren’t enough. Once you start diving repetitively over multiple days, you’re primed to get the benefit from this training.
If that is not you yet, then just wait… it will be