28% O2 vs. 32% O2: What a Difference

[Mike Edmonston]

Just plan your dives to a 1.2 - 1.3 PO2 with 1.6 (100% o2) for deco. Depending on your average and max depth, your mix will vary. I use between 30% and 32% for Ginnie Diving.

Safe Diving

[TonyDCaver]

I just had this explained to me the other day... But what if you were told that O2 is more narcotic then N2? Not by much, but it is....



Apart from helium, all gases that can be breathed have a narcotic effect, which is greater as the lipid solubility of the gas increases

[MORGAN]

When nitrox made its way into the recreational realm in the mid-90s, there were a number of "benefits of nitrox" touted. You'll feel less tired after a dive. You'll feel less cold during a dive. You'll be less narced during a dive. As time went by, each of these were disproved in blind tests. ... I'm old, and I want to get older.

As a fellow 1958 model, I cling to the idea that "geezer gas" reduces fatigue! Don't go bursting my (Nitrox) bubble!

I forget who said it - "The great tragedy of science - a beautiful theory destroyed by an ugly fact."

Mike

[BobK]

Just plan your dives to a 1.2 - 1.3 PO2 with 1.6 (100% o2) for deco. Depending on your average and max depth, your mix will vary. I use between 30% and 32% for Ginnie Diving.

Safe Diving

I agree. I've been moving down to 1.3 max PO2s. Just seems safer and isn't that much different for deco.

[Jay]

As a fellow 1958 model, I cling to the idea that "geezer gas" reduces fatigue! Don't go bursting my (Nitrox) bubble!

I forget who said it - "The great tragedy of science - a beautiful theory destroyed by an ugly fact."

Mike

I agree, as another 1958 model.
I notice a significant difference, especially on multiple dives a day. It could be an individual physiology thing, as most gas related issues are.

Forrest hit the nail on the head about the 34% a few years back. There was a death at Devil's and I believe a few other incidents, not death's, at Little River in the same period. It may not have been necessary for everyone to switch from 34 to 32, but it seemed like the prudent thing to do. I had some friends who backed down to 32 % for LR. For some reason, I never had a problem at Ginnie, but I had some O2 issues at LR on 34%, long O2 deco's.

[Rick Palm]

All of these points are well-taken. It doesn't make sense to trade nitrogen for oxygen for a dubious decrease in narcosis, and less deco time: The complications of O2 toxicity are certainly a lot worse than N2 toxicity. My bet is that even helium has some narcosis associated with it: that's the way it seemed to me in the back of DiePolder III several years ago. With limited PO2 and PN2, that was the only explanation.

Of course, perhaps it is all because I have a lower mental status to begin with!

But I agree with all of the assessments above: better to put up with the inconveniences of a higher PN2, than risk a potentially fatal O2 hit. I'll stick with 32%.

(Incidentally, I don't consider the Devil's Ear/Eye system a "high flow" system, if you know where the sweet spots are!)

[Sludge]

Don't go bursting my (Nitrox) bubble!

My friend Ron and I were discussing this several years ago. I was wondering where this "myth" started, and he actually had an answer. He said some tests were done where divers would make a dive and deco on air, then the same dive on nitrox with deco on oxygen. The longer the dive/deco, the more pronounced the difference between how tired the divers felt.

Of course, he didn't provide any references...

[wingman]

I just had this explained to me the other day... But what if you were told that O2 is more narcotic then N2? Not by much, but it is....



Apart from helium, all gases that can be breathed have a narcotic effect, which is greater as the lipid solubility of the gas increases

Looks like i'd like to brew up a little xenonox for the next galaxy dive at ginnie...if i could only afford that...a little pink floyd (comfortably numb) on the uw ipod and a dive to remember (maybe).

[Jay]

Looks like i'd like to brew up a little xenonox for the next galaxy dive at ginnie...if i could only afford that...a little pink floyd (comfortably numb) on the uw ipod and a dive to remember (maybe).

Now people will be huffing Xenon bulbs.

[sskasser]

My friend Ron and I were discussing this several years ago. I was wondering where this "myth" started, and he actually had an answer. He said some tests were done where divers would make a dive and deco on air, then the same dive on nitrox with deco on oxygen. The longer the dive/deco, the more pronounced the difference between how tired the divers felt.

Of course, he didn't provide any references...

Simply spending more time in the water, as with air, might have something to do with perceived "tiredness" as well.