Three things you need to know about Enriched Air Nitrox
Enriched Air, Nitrox, EANx. What is it? Is it safer than air? Are there any new or different risks? Does it change how I plan a dive? Let’s take a look at Enriched Air Nitrox and try to answer those questions.
What is Enriched Air/Nitrox? Nitrox is a shortened name for nitrogen/oxygen. Nitrox is a term that can be applied to air (roughly 79% nitrogen, 21% oxygen). Nitrox can also apply to a different mixture. Enriched Air, Enriched Air Nitrox or EANx is a name for a breathing gas with a higher percentage of oxygen. There are a few different ways to blend enriched air. For recreational use, we typically use a blend somewhere between 22% and 40% oxygen.
Is Enriched Air Nitrox safer than diving with air? Dive computers and dive planners (tables, etc) are designed to track how much nitrogen your body absorbs while on a dive. They also take into account how much nitrogen you off-gas when you’re on the surface. The goal is to keep nitrogen levels in your body to a point where bubbles won’t form and cause decompression sickness. It seems logical that if we remove some of the nitrogen and replace it with oxygen, that means there is less nitrogen for our bodies to absorb, so the decompression sickness risk should be reduced. There is a trade-off, though. Oxygen, when breathed at depth, can cause other problems. The biggest risk for a diver on a dive is central nervous system oxygen toxicity. The nutshell version is that if you breath oxygen at too high of a partial pressure, you can have a seizure underwater. Usually oxygen-induced seizures are self limiting, but when you’re underwater, you might drown. So, what does that mean? It means you can’t dive as deep as you can on air, but you can make longer dives because you aren’t absorbing as much nitrogen.
How does dive planning change? As mentioned above, you can make longer dives, just not as deep. But how to plan that? If you’re using a table-based or software-based dive planner, you’ll need to adjust for the blend of enriched air that you’re using. There are some “standard” blends and you can find tables specifically for them (32% and 36% oxygen). Otherwise, it takes a bit of math to convert your depth to an equivalent air depth and then use your dive planner. The easier way is to use a dive computer. You just need to know the percentage of oxygen in your enriched air and how to program your dive computer. After that, your dive computer plans the rest. Be careful, though, since some dive computers will reset after being on the surface for too long. Some computers will also reset for an impossible blend (like 50% oxygen, while keeping the shorter, air-based time limits) in an effort to keep you safe. Be sure to read your computer’s instruction manual.
There you go. Three things about Enriched Air/Nitrox. Want to try it out? Contact me and we can arrange a Discover Enriched Air dive or you can complete the full Enriched Air Diver specialty certification course. Need some more info first? Check out the info at PADI.com. There’s also an eLearning option for the specialty.