Should you be diving NITROX if you can not answer these questions?

[Van Isle]

I think (in this "non-prejudiced" snippet of context) that perhaps the "2nd" poster was trying to ascertain what the OP's perceived value was in using nitrox at 130'. At 70-90 feet the advantages are pretty obvious, but what's the bottom time gained on EAN32 vs air at 130 before NDL? 4 minutes? And all that time CNS clock is running, and you're at 1.6 ppO2...

I think that's what the "2nd" was trying to ask of the "1st."

I'm not sure what your point in this thread, is, though.

VI

 

[tomboyy]

technically a 19% O2 81%N is still nitrox. That mix at a ppo2 of 1.6 is 245fsw. So I guess there Is not really a limit as long as you are OK doing lots of really long deco stops on the way up.

Yaaa... I plugged the numbers in, at 245 you'd convulse and die.... if you stayed at 244.8947368 ' your good

 

[pittyyofool]

Yaaa... I plugged the numbers in, at 245 you'd convulse and die.... if you stayed at 244.8947368 ' your good

plug the numbers in that is cheating... what happened to long hand math?
I cant right the equation here because It would make it to easy for someone to figure out the answer to the OP. but believe me you can do it with jr.high math skills.

 

[Dtaine]

quite possibly, If one plays with Fire to long they are sure to get burned.

Well, if you want to try and figure out your personal tolerance to oxygen toxicity that's fine because it's your life on the line. I'm just suggesting that 1) you'll never have a definitive tolerance and 2) the types of experiments you've done are essentially useless.

As far as the original question goes, someone who dives nitrox should be able to perform the basic calculations involved.

 

[Blackwood]

25/25 is a perfect mix for 150'. And by most recreational definitions, if the 02 component is > 20.9% then it's Nitrox. (Semantics I know)

By any definition I've seen, if it contains gases other than Nitrogen and Oxygen in more than trace amounts, it's not nitrox.

In any case, I get narced at 100 feet on air (at least in the conditions in which I usually dive), and 150 on 25/25 is like 100 on air. Personally, I'd rather a little more helium and a little less oxygen, since adding the former doesn't hurt (wallet aside) and subtracting the latter is a more conservative (tox).

To me, toxicity and narcosis are the biggest concerns from a gas selection standpoint. Deco is what you live with after addressing the primary considerations.

 

[Reg Braithwaite]

So.. how deep can ya go on "nitrox"

142' on Tx 21/0:

YouTube - Reino Magico - Isla de la Juventud - CUBA

 

[DaleC]

Some snippets from another thread - all posts were made by three different people all of which are NITROX certified. The third post is mine which is combination of two posts.


First Post - "I was diving ... at 1.6 ppo (130?)"

Second Post - " ... what where YOU doing at 130 ft on NITROX? What was your %? If you planned on going THAT deep, why use nitrox? What was the benefit of nitrox at that depth?

Third Post - "Do the math, the first post contains all of the information needed to figure out the mix. As for using NITROX at 130 feet there is nothing wrong with it and the benefits to diving NITROX at 130 feet are the same and more as diving it at 60 feet. If you do not know this or can not do the math you should not be diving NITROX"

Several people did not get my post - what I found odd was that these posts were part of a larger accident discussion on this board where many people were stressing personal responsibility in the context of a person who had some knowledge but perhaps not enough to not keep/get themselves out of trouble. Yet IMHO the second post shows someone who has had the training yet still fails to have the knowledge.

So if you are nitrox certified could you answer the questions to the second post without looking them up? Please do not post the answers as they are not german to the thread and might prevent someone from realizing they need a refresher course.

I'm not sure I understand the question correctly.

The mix with that O2pp at that depth is perhaps the most common banked mix used so familiarity may lead one to memorize that data. Is that a reliable gauge of Nitrox working knowledge or would the ability to use the tables correctly, no matter the mix, be a better determinate?
I don't approach Nitrox from a memorizing/formulaic POV anyways as the values are static. I analyze the mix, look it up on the tables and mark the MOD on the tank. The MOD doesn't change after that. My brain is too old and feeble to remember formulas I won't use but I can reliably calculate the MOD's for any mix which is about all I need to do (aside from the daily % that is).

From the tone, the second post was mainly rhetorical in nature with (ahhh) a touch of the zealousness of the newly converted.

 

[The Kraken]

I'm sure I'll get stomped on here, but here goes anyway . . . .

PPO's are "RECOMMENDED".

We seem to be in an era of "less is better".

If I recall correctly, when I took my nitrox course it was posited that a PPO of 1.6 was the level which was recommended that a diver not exceede because beyond that level the possibility of oxygen toxicity was more POSSIBLY likely to occur.

For some reason, the 1.6 PPO seems to be interpreted nowadays as the level at which O2 toxicity WILL occur if the diver exceeds it.

I agree with prudence, caution, safety and so forth, but there comes a time when being safe becomes being paranoid.

I can understand not diving beyond 1.5 or 1.4, but when we start getting to PPO's of 1.2, or 1.1, or 1.0???

What's next???

Let's not dive beyond 0.5, that way we'd be really safe.

I have no compunction about diving a PPO of 1.6, although I prefer, for safety's sake, 1.5 or 1.4.

But, in my opinion, going to such reduced percentages of O2 effectively negate the rudimentary reason for diving nitrox.

Just my opinion.

the K

 

[The Kraken]

Come to think of it, the best way to avoid O2 toxicity is by not diving at all.

the K

 

[Reg Braithwaite]

Come to think of it, the best way to avoid O2 toxicity is by not diving at all.

I usually breathe a mix with a PPO₂ of 0.21 during surface intervals to help off-gassing. Am I being too conservative?