Nitrox isn't new: its origins date back a century, specifically to the First World War period, when it was used for military purposes. However, Nitrox didn't enter the recreational diving community until the early 1990s, though its use is now widespread.
Here you can find some enriched air diving courses.
While you likely know of or have heard about it, you might not be entirely clear on what Nitrox is or its purpose. Below, I'll explain the most important aspects in the simplest terms possible.
Nitrox refers to any nitrogen-oxygen gas mixture. Thus, standard air is a normoxic Nitrox mixture composed of 21% oxygen and 79% nitrogen. There are also Nitrox mixtures with higher or lower oxygen content than air, referred to as hyperoxic and hypoxic Nitrox mixtures respectively.
Therefore, although in recreational diving the term "Nitrox" is commonly used to mean "enriched air Nitrox" or "hyperoxic Nitrox", it's important to understand that while all enriched air is Nitrox, not all Nitrox is enriched air.
Each Nitrox mixture has its own advantages, so which one to use depends on several factors.
Type of diving to be undertaken:
Hypoxic Nitrox offers advantages regarding depth; hence it's widely used in medium-to-deep diving. This is because, being oxygen-depleted, the maximum PPO2 (Partial Pressure of Oxygen) is reached at greater depths.
In other words: at the same depth, there would be less risk of oxygen toxicity with hypoxic Nitrox than with air. This mixture isn't common in recreational diving but is in technical diving, where hypoxic Nitrox combined with Helium forms the mixture called hypoxic Trimix.
Conversely, hyperoxic Nitrox, known in recreational diving by the term EANx (Enriched Air Nitrox), offers some advantages regarding dive time. As it contains less nitrogen than air, it reduces the diver's nitrogen exposure, meaning that for the same dive profile, tissues take longer to saturate and thus the NDL (No Decompression Limit) takes longer to reach.
This is particularly beneficial for successive dives or surface interval times, as with less nitrogen in our system, we can do more dives for longer compared to using air. The trade-off is that being richer in oxygen, the PPO2 occurs at shallower depths, limiting our maximum depth.
Within a hyperoxic Nitrox gas mixture, the oxygen percentage can vary. Therefore, the EANx nomenclature is always accompanied by a number indicating the oxygen percentage in that mixture. For example, EANx32 means enriched air Nitrox composed of 32% oxygen and 68% nitrogen.
All certification agencies offer specific courses for using different gases and combinations. Proper training before using these gases is crucial for divers - so much so that no dive centre will allow divers to use gas mixtures without proof of required training.
If you have any questions about gas mixture diving training, consult your Dive Instructor: they'll know how to advise and guide you.
