Sunday, December 17, 2006

Nitrox Rox!

Enriched Air Nitrox (EANx) is usually just referred to as Nitrox. Not to be confused with Nitrous Oxide, nitrox refers to a blended breathing gas made from mixing air with pure oxygen. It's popular amongst recreational divers who are properly trained and qualified to use it.

Nitrox is popular as an alternative to air for a number of reasons. The increased oxygen replaces a significant portion of the nitrogen in normal air. Nitrogen uptake into body tissues is the limiting factor (besides air supply) for how long a diver can remain at a certain depth. By using nitrox a diver can choose to either:

  1. Stay longer at that certain depth than air would allow, or
  2. Spend less time between dives off-gassing excess nitrogen, or
  3. Dive to the standards for air with an even greater safety margin.
Either, or, or, but not all three.

Aside from what the textbooks say, most nitrox divers also report feeling less tired after a day of multiple diving and multiple dive days. I know that a few short air dives tire me out in a way multiple long nitrox dives don't. Given the choice, I always pay the extra for the chique breathing mix!But nitrox comes with it's own dangers. And thus every tank and piece of equipment used with nitrox must be prepared for it's use, and must be labelled to warn untrained divers not to use it. The issue with nitrox is that it brings a problem of the deep up to recreational levels.

At about 220 feet down, air is toxic to humans. The "partial pressure" of the oxygen in the air is enough to cause blackouts, convulsions, trouble thinking, tunnel vision and more. But 220 feet is way deeper than recreational divers are allowed to / trained to go, so issues of oxygen toxicity aren't taught.

Adding oxygen to the breathing mix not only displaces harmful nitrogen, but also raises the depth at which oxygen reaches a toxic partial pressure. This can put it into the range of depths a recreational diver might plan to reach. So the specific maximum depth for a specific nitrox tank is something the diver using it must measure and calculate.

Breathing nitrox underwater is no different from breathing air. Other than remembering to avoid your specific maximum depth, there is no difference in taste, smell, sensations or otherwise. Only the analysis of the tank's mixture and the calculation of the limits are different from diving with air. (And making sure your equipment is appropriate.)

These issues are now taught in "classroom only" nitrox certification courses. You can study scuba in the dead of winter and not get wet or cold. (Like a dry suit.)

For those interested, contact your local scuba shop. Breathing air is nice for land. But adding oxygen makes scuba even more fun.

No comments: