Accumulated 02 following a large number of repetitive Nitrox dives over 3 days.

[Astran]

If you had responded to some of the questions regarding your next set of dives under similar conditions with:

• I will use tables to follow my O2 exposure and use my Oceanic computers as back-up devices; or,
• I will buy a different computer that does not use a theory based on a 24 hr rolling window, but a computer that uses a theory similar to the Shearwater programming (02 half-life);

I would have thought you to be thinking logically (even though I would not take those actions).

As it is, I am not witnessing responses that are rational and logical.

It is illogical and irrational for me to purchase and carry and maintain a dive computer which is for the sole purpose of ensuring that when my Oceanic computer indicates a high 02 level that this other less conservative computer is remaining silent and not complaining because I'm not close enough to the 02 limits and never will be close enough to the limits during no-deco, recreational single tank diving on EAN >40% for this other computer to be of any use as has been clearly proven by several posters on this thread.

 

[rjack321]

I was aware in advance of the dives that I would not exceed the MOD but it would be close on a few of the two dives. In fact I had no control over which blend I was using as the rental tanks were supplied by the Dive Ops and I didn't want to go to the trouble to rent tanks with a higher blend elsewhere (on the day we were diving EAN 32 on a wreck that sits at around 115').

you wanted more O2 than EAN32?

 

[Astran]

you wanted more O2 than EAN32?

Yes on the dives we did on Friday, we were provided with EAN32 but I would have preferred EAN36 as the maximum depth was about 110'.

 

[rjack321]

Yes on the dives we did on Friday, we were provided with EAN32 but I would have preferred EAN36 as the maximum depth was about 110'.

you were already right up against the O2 limits..
this would have made your oceanic alarm even sooner but I guess if you are just going to ignore it what does it matter.

 

[Astran]

you were already right up against the O2 limits..
this would have made your oceanic alarm even sooner but I guess if you are just going to ignore it what does it matter.

It's my understanding from some of the more comprehensive, technical posts on this thread complete with calculations that despite the Oceanic screaming at me because of it's ultraconservative algorithms that do not account for half-life metabolism of 02, I was in fact not close to the 02 limits at all- which are almost impossible to achieve if not impossible, with single tank recreational nitrox diving.

 

[rjack321]

It's my understanding from some of the more comprehensive, technical posts on this thread complete with calculations that despite the Oceanic screaming at me because of it's ultraconservative algorithms that do not account for half-life metabolism of 02, I was in fact not close to the 02 limits at all- which are almost impossible to achieve if not impossible, with single tank recreational nitrox diving.

you completely missed the part about CNS and pulmonary limits being different

there are 3 parts to oxygen and nitrox use
the depth mod
the CNS has a 90min half-life while the oceanic uses a 24hrclock
the daily pulmonary limits do not have a half life - and you exceeded those

 

[Astran]

you completely missed the part about CNS and pulmonary limits being different

there are 3 parts to oxygen and nitrox use
the depth mod
the CNS has a 90min half-life while the oceanic uses a 24hrclock
the daily pulmonary limits do not have a half life - and you exceeded those

Hmm. I didn't get that impression from those more technical posts to which I am referring.

I didn't hit a P02 of 1.4 at any time during the week, and I think it's fair to say that I averaged closer to P02 of 1.0 to 1.2,. Referring to the table in the link below from DAN, gives a daily 02 exposure limit of 210 minutes (normal exposure) and 300 minutes (exceptional exposure) which is far more than I did in any 24 hour period during those 3 days. I count 251 minutes total dive time in the most active 24 hour period, in fact I was at P02 1.03 at the time I received the warning on my computer and the levels dropped to .95 during the duration of the dive.

OXTOX: If You Dive Nitrox You Should Know About OXTOX — DAN | Divers Alert Network — Medical Dive Article

 

[tursiops]

Hmm. I didn't get that impression from those more technical posts to which I am referring.

I didn't hit a P02 of 1.4 at any time during the week, and I think it's fair to say that I averaged closer to P02 of 1.0 to 1.2,. Referring to the table in the link below from DAN, gives a daily 02 exposure limit of 210 minutes (normal exposure) and 300 minutes (exceptional exposure) which is far more than I did in any 24 hour period during those 3 days. I count 251 minutes total dive time in the most active 24 hour period, in fact I was at P02 1.03 at the time I received the warning on my computer and the levels dropped to .95 during the duration of the dive.

OXTOX: If You Dive Nitrox You Should Know About OXTOX — DAN | Divers Alert Network — Medical Dive Article

Nevertheless, he persisted.
You can't work out toxicity dangers using average PPO2s; the curves are not linear. A few minutes at 1.3 are a lot more important than many minutes at 1.0, not just 30% more important.

 

[Astran]

You can't work out toxicity dangers using average PPO2s; the curves are not linear. A few minutes at 1.3 are a lot more important than many minutes at 1.0, not just 30% more important.

Again, I rounded UP. To a P02 1.3 even though I clearly was below that level for much of my diving. At P02 1.2, according to the DAN article, a diver has up to 300 minutes per day maximum exposure, and I dived a total of 251 during the most active diving/24 hour period of the trip. For much, or even most of that time my P02 exposure was significantly lower, as I stated earlier I was at 1.03 when my computer's 02 alarm activated and rapidly dropped to .95.

Subtract about 18 minutes for 6- 3 minute safety stops at 15' and you're down to 233 minutes total for that high dive volume 24 hour period.

 

[DBPacific]

Interesting. I must admit I never really looked into the actual differences, I just assumed

This seems to be a theme with you. If you don't and won't listen to your computer or advice you don't like, what exactly is your purpose on this thread? Your questions have already been answered. I am very curious as to where, when, and from who you learned nitrox