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PADI Enriched Air Nitrox Course November 7, 2008

Posted by Chris Sullivan in Training.
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I took the PADI Enriched Air Nitrox course during my trip to the Turks and Caicos. I’d already taken a Advanced Open Water Diver Course, Rescue Diver Course, and part of a dry-suit course that year and so was well into my 3 year training binge, and when one of the instructors at Caicos adventures suggested I try it, I jumped.

Caicos Adventures had a membrane system which compresses air against a membrane that allows more Nitrogen to escape than it does Oxygen, effectively enriching the mix. These systems are good to about 40% concentration, and this one was permanently set to 32%. So they could fill a tank with 32% Enriched Air without having to have it Oxygen cleaned first. This is ideal for an island operation, and they could actually run their hoses from their compressor on shore right out to their boat, saving the backs of their workers.

The course itself involved reading the book and filling out the knowledge reviews as usual. The  next day I met with the instructor after the day’s diving, and we went through the material. He was surprised that I already understood it, telling me that it sometimes took him hours to help students understand it.

I’m fairly mathematically inclined (though not brilliant at it, like others I’ve known) and so find diving math pretty simple. It is really mostly interpretation of tables, which are set up exactly like the PADI DSAT Air table but with different numbers to reflect the different mix.

The course covered Safety, Equipment, Oxygen Exposure Calculations and Limits, Analysis and Enriched Air Filles, using Computers (one of which I’d just bought), Emergencies, Using the standard RDP with Enriched Air, using the special Enriched Air RDP, Managing Exposure with the Equivalent Air Depth and Oxygen Exposure Tables, and using Formulas.

On the last topic, the instructor asked me if I could use the Maximum Depth Formulas. The first, for maximum depth (1.4 PP02 max), is (46.2/PP02)-33. I told him that yes, 46.2-33 feet, or 13.2 is the depth at which you reach 1.4 PP02 on pure Oxygen, and that the formula just adjusts that for whatever fraction of Oxygen that was being breathed. It was a very short session.

At the time, the course required you to do 2 dives on Enriched Air. There’s not much to it, unless you don’t know how to use a dive table. Anyway, I did the dives and got the certification, and haven’t used the table since, as my computer does everything I need. I have also used desktop decompression software to compute custom tables for technical diving, but that came a bit later in this story.

So what’s it good for? For one thing,  when on a dive trip I always use Nitrox on my last day of diving (the one before I fly). I do this just to be more conservative with the flying after diving guidelines, although my super cautious computer sometimes takes 24 hours to clear even with the Nitrox. On one trip it cleared while the plane was taxiing for take-off. Also if I’m doing more than 2 dives in a day I’ll do the last two with Nitrox. On air, I typically will go into decompression for a few minutes on my second dive unless it is very shallow, as in warm water my air lasts a long time, so using Nitrox allows me to stay further from the edge.

Back at home, Brad often gives me Nitrox fills for free, especially when his O2 tanks are running low (we have a partial pressure system at the shop, requiring us to have O2 clean tanks). In fact, I’ve only been charged twice for Nitrox there, once when Brad wasn’t around and the other time when I needed 68 cubic feet to fill my an AL80 deco tank with 80 percent mix. He still gave me another tank of 50 mix for free. I try to pay him back by doing a little open water student supervision for free.



1. Lynda Lippin - November 9, 2008

I’m glad you did a different dive training while you were here that you still find useful. This is one of the first posts I’ve seen a while commenting on Caicos Adventures (a really nice group of people who know what they’re doing), so Thanks!


2. deepstop - November 9, 2008

Hi Lynda. Yes, it was a precursor to a whole slew of other training, including a very intensive wreck diving course (which I now help teach) and a deep diving course. Caicos Adventures did seem like a good bunch – one day we found a Conch fishing boat that had conked out, and we towed it back to the island.


3. deepstop - November 9, 2008

Those of you with Gas Blender experience might think that 68 cu feet is too much for an AL80 to be filled with EAN80. You’d be right. Unless the tank was topped off with pure Nitrogen instead of air, slightly less Oxygen would be required. Given all the free stuff I get from the dive shop I always ignore these little errors.


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