If I have to do any of my reevaluation dives in Ginnie, they'll be on 30% -- helium :)
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If I have to do any of my reevaluation dives in Ginnie, they'll be on 30% -- helium :)
If I am doing multiple stages (therefore longer exposure to cns clock and otu's), or we have a flood (to a max depth of 110' after that I like a little HE), I cut it down to 28%.
The floods are a time when the shops should definitely cut the O2 back.
When we was at Little River last month, we had them top off with air instead of 32%. I dont like running the limits that close. I could see 30% being a good choice at JB and Ginnie as well.
I don't think it's a big deal at Ginnie, at least in the places I go. 100 ffw with 32% gives about a 1.28 PPO, which is perfectly sane.
Actually, for myself, I prefer to dive 32/30 there. No, it's not a standard gas. But so far so good :-)
I think it all depends on the amount of time your going to be in there. I just did a dive in Ginnie that went near 4hrs by the time deco was over and I ran 1.2 (approx 30%) all the way in and 1.3 (approx 32%) on the way out with pretty much everything from the catacombs out at 1.4. At the end of the dive my CNS according to the computer was 102% but when I hit deco I was less than 80 so I'm fine going over on CNS if I'm in a relaxed deco environment (sleeping in a crack in the eye).
It's all personal choices and there is a lot that factors into it and your reactions could vary from day to day. All that said, I'd go with 32 and wouldn't give it a thought if I was doing 1-1.5 hr run times two or three a day at Ginnie for a weekend.
Maybe it's "perfectly sane", but wouldn't 30% be even more so? For me the extra risk is not worth a few extra minutes of hang time.Quote:
Originally Posted by BobK
I have stated my reasons for the 30%, I am curious what yours are for the 32%.
Quote:
Originally Posted by Marc Bryan
Okay I’m going to preface this by saying Ox Tox underwater is a really really bad thing and would be worse than DCS on any day. That said…
Navy divers in water recompression treatment includes O2 exposures to just shy of 3ATA (I beleive 60 FSW is the switch but it's been a long time sense I've looked at the tables it could be deeper). Chamber rides can also hit a 2 during their runs depending on what they are treating. OTU/CNS is just like any other dive/deco table and very conservative for 99% of the population on 99% of the days they dive.
If you want to dive 30% good on you, if you want to dive 32% good on you to. I personally like higher PPO2 and lower PPN whenever possible for narcosis and deco (I don’t mind deco but if something comes up I’d rather be able to get out sooner). I’m even known to throw some HE in there even on shallow stuff just to make work of breathing easier among other things.
Most fill stations bank 32%, but most will also pump whatever mix you want. FYI, EE banks 30%, with 30% helium.Quote:
Originally Posted by Marc Bryan
It is up to you do decide what mix is right for you. Until the majority of divers request 30%, the fill stations will bank 32%.
Dives are getting longer => percentages getting lower.
Marc,Quote:
Originally Posted by Marc Bryan
There is one shop (really close to you) where the analyzer almost always says 31 percent on my tanks when I check it, which I think is good.