Posted by Karl S. on June 29, 2003 at 15:19:43:
Having gone through the entire TDI training package for technical scuba, I have now gained a new appreciation for Nitrox.
In the Advanced Nitrox course, you learn to use various mixes of Nitrox up to EAN80.
In the Stage Decompression course, you learn to use EAN36 or EAN80 as decompression gasses. You could decompress with air, but you learn that decompressing with Nitrox is more efficient and faster. You usually carry only one deco tank on these dives, so that you cannot accidentally kill yourself by breathing the wrong Nitrox mix at the wrong depth.
In the Extended Range course (aka Advanced Deep Air to the IANTD group), you learn to cope with simple underwater tasks in the realm of narcosis, and you also decompresing with Nitrox. You could skip this phase and move on to Trimix, however there are places in the world where you cannot get trimix, and therefore you learn to appreciate Trimix even before you ever dive with Trimix from this Extended Range course.
I am not going to argue for or against Extended Range / Advanced Deep Air training. I will simply let TDI and IANTD argue it instead.
In the Basic Trimix course, you learn to dive with TMX 18/30 to 200 ft and decompress with Nitrox. This 18/30 mix does not require a travel gas, so you cannot kill yourself underwater by switching too late from the travel gas, which would normally be one of your deco mixes, the leaner mix. The 18/30 mix at 200 ft is a fairly narcotic mix, by modern standards, so you are benefitted by having suffered through the Extended Range course earlier.
In the Advanced Trimix course, you learn to dive with TMX 15/40 to 250 ft and decompress with Nitrox. This 15/40 mix is also somewhat narcotic compared to more modern mixes. And it too does not require a travel gas, but you learn to get down your 10 ft bubble check fast so that you do not breath too much TMX 15/40 on the way.
The KEY CONCEPT of all this training regarding Nitrox is simply this: that Nitrox is in fact a decompression gas. Plain and simple, truth be told, it is a decompression gas.
And with a pair of doubles and at least 5 other scuba tanks crying for O2 cleaning now, each year, I have to ask myself the question, is it really worth it each year to have all 7 scuba tanks O2 cleaned for Nitrox??
AND even more generically, is it really worth it to dive with Nitrox as a primary breathing gas at any time?
I suppose you could argue from a technical perspective that since we use EAN36 as a travel mix to depths of 100 ft or less, then that in itself endorses Nitrox as a regular diving mix, even for NDL diving.
On the other hand, you could also argue that the main benefit of Nitox is in fact as a decompression gas for deep air and helium-based scuba diving, and not as a primary breathing mix.
Maybe the truth is a hybrid of both arguments, that air is a better mix for dives that are either short in duration or shallow in depth, and that Nitrox is not a benefit unless you are diving for a long duration or diving deep. So as long as you keep the deep portion of your diving short in duration, and the rest of your diving shallow, say less than 50 ft deep, air is prefectly good for your scuba diving.
In that case, I can agree with Ken Kurtis, that compressed air is fine for most if not all of your scuba diving.
As for myself, I have gone back to diving with compressed air for the first dive of my diving day. And if I dive a second dive, which is rare unless I am on a boat, then I dive with EAN36 and keep my depth shallower than 100 ft on my subsequent dive(s).
Most dive boats here in California and around the world allow you to order Nitrox if you please. And it pleases me to dive my second and subsequent dive(s) of the day with EAN36. But I shirk internally when I see other divers diving their first dive with EAN36 or even EAN32, when compressed air would do just as well.
In my mind, EAN36 is really primarily a decompression mix as well as a travel mix for really hypoxic helium mixes. I do not understand why the recreational shallow-diving crowd started diving Nitrox, when for most diving, compressed air works just as well. Especially on the first dive of the day. Especially then.
Arguments and viewpoints to the contrary are welcome. Ad hominem arguments inherently carry their own refutation.
Now, having said all that, I can get back to searching for those sunken Spanish treasure ships off our beautiful California coast!
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