Nitrox question?

debajo agua · Jan 21, 2012

From my book:

"In terms of susceptibility to O2 toxicity, the actual variation among individuals, or from one day to the next, may be as great as 13:1."

What does it mean?

TIA

Rhone Man · Jan 21, 2012

I have no idea. What textbook is that? Is there something in the context which suggests what they might mean?

It is certainly true that O2 toxicity varies wildly, but I have no idea what the ratio 13:1 might mean. It is not a variability ratio (and even if it were, the effects of O2 toxicity are not sufficiently well established to produce one).

diverrex · Jan 21, 2012

I suspect that the author is making the statement that the 1.6 oxygen toxicity number is not hard and fast but some individuals haved toxed at something less than 1.6 while other have gone well past 1.6 without any negative results. How they come up with the 13:1 ratio I have no idea.

debajo agua · Jan 21, 2012

SSI's EAN Chapter 2 page 14

Here's the whole paragraph:

"In terms of susceptibility to O2 toxicity, the actual variation among individuals, or from one day to the next, may be as great as 13:1. Fortunately, NOAA's working-diver limits are conservative and - while they cannot guarantee 100 percent safety - they nonetheless substantially increase one's safety margin."

Jim Lapenta · Jan 21, 2012

What it seems they are saying is that your chances of toxing can be as much as 13 times greater from one day to the next. Although I have no idea where they came up with that figure. I've never seen it any of the materials I've used or read and those include nitrox books from 4 different agencies, 3 other on the subject in general, and the NOAA manual as well as US Navy manual unless I missed it in there somewhere.

agilis · Jan 21, 2012

Something is missing. A variability of 13:1 comparing what to what? I think a ratio requires specified components
.

Griffo · Jan 21, 2012

I remember reading that in the SSI book and wondering the same thing - how the hell had they come up with that number? I mean, does that mean on a good day I could handle a PO2 of 16.9? I think not!

Mind you there were also a lot of errors with the version of the Nitrox exam I had with SSI, so I just discounted that value as either a mistake or some theoretically useless statistic.

ianr33 · Jan 21, 2012

I'm guessing it's time to tox at a given pO2. e.g. one subject toxed after 10 minutes,another took 130. ?

Point is the variation is huge,even for the same individual on different days.

Thalassamania · Jan 21, 2012

Strikes me as as stupid number. Your guess is as good as mine: how about, "a ppO2 of .21 is fine and unlikely to tox but 13 times that (ppO2=2.73 or just shy of 60 feet) may be problematical?"

Tortuga68 · Jan 22, 2012

Well the deep air record is 155m, so that's PPO2 of 3.465 where someone didn't tox, but then 1/13th of that would be 0.26 and I'm not aware of anyone toxing at that low partial pressure... on that basis 7:1 would seem more reasonable, but it doesn't account for exposure anyway

Nitrox question?

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debajo agua

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agilis

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