What Is Enriched Air Nitrox

The Components of Enriched Air

In the broadest sense, Nitrox is any gas blend of oxygen and nitrogen. Air, of course, is basically a nitrox mix of approximately 21 percent oxygen and 79 percent nitrogen. For divers, enriched air Nitrox is any gas blend with more than 21 percent oxygen. Generally for recreational divers this is a blend of either 32 percent or 36 percent oxygen, sometimes abbreviated EAN32 or EAN36.

As we all know, nitrogen is the cause of decompression sickness. In our PADI Open Water Diver course we learned that our bodies use up oxygen when we breathe. However, because nitrogen is not used by our bodies, nitrogen saturates our tissues. This happens whether we are on the surface or on a dive.

Our regulators are designed to deliver air to us at whatever pressure we are at. That’s why our bottom times become shorter and shorter the deeper we go. As our regulators deliver more and more air to us as we descend, more and more nitrogen is absorbed into our tissues. The more nitrogen we absorb on a dive, the more dangerous and difficult it becomes for us to return to the surface.

Why? While we can tolerate some excess amounts of nitrogen in our tissues, exceeding the safe limits prescribed by our dive tables and computers can result in the dissolved nitrogen in our tissues coming out of solution on ascent and forming bubbles that produce symptoms such as joint pain, coughing, rashes, headaches, paralysis, unconsciousness, or worse. This is what we divers call decompression sickness and our non-diver friends call the bends.

By reducing the amount nitrogen in our breathing gas, we do not absorb as much nitrogen on our dives. Gas blends with just 32 percent or 36 percent oxygen can sometimes nearly double the time a diver can spend at depth before reaching the safe limits of excess nitrogen.

In addition, because we absorb less nitrogen on our dives, even if we do not stay down longer than air would permit, enriched air can shorten our surface intervals and still give us enough time to enjoy the next dive. In some cases, we can actually do more dives in a single day using enriched air than we could safely do if we dived with air.