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As the director of that project and the OCDA, I'll convey our 'break' method
for that particular dive (even though most all of them are done virtually the
same)
On the dives we conducted at Maramec (and all dives made up here by the
OCDA), we use a very low PO2 for bottom gas (sometimes not even a 1.0) with a
high He content (45%-55% depending). Stage gas is the same *or* with a
slightly reduced He content for shallower depth and deco situations.
Our deco gases are like this, O2, EAN50, EAN35, and Tmx 20-30.
If some Tmx is left over from the stage(s) following the 1st stages of
deco, we also use it to 'break' during the rest of deco (a good way to use
the gas you'd drain afterwards anyway). The 'break' PO2 is very low and
keeps the potential O2 problems to a minimum (as you know, the whole reason
for breaking). In the 'written' case, we had some 20-20 left and used it to
break while saving the back gas/deep safety's ((We did the whole dive,
incidentally, on stages with minimal back gas usage ( 300psi)).
The longer type dives up here are currently limited by water temperature,
and our dives are not nearly as long as George, etc. are making. Most of our
methods, etc., are the result of direct consultation with George, too.
Also, our break intervals are 20 to 5 and we haven't had lung burning
problems to date (duration may be the reason).
Finally, I really don't think the OCDA guys/gals are strokes.--Jason
kirvine@sa*.ne* wrote:
> Higher is better - easier to breathe. Remember you are also trying to
> offset swelling and irritation. Also adding helium is preferable to
> adding nitrogen at that stage, since it is less lkely to conribute to
> bubble growth when you get out. I use the lowest oxygen that can be
> breathed at the depth with the highest helium. The term "air break" is
> generic for this action. Most people just don't get how to use oxygen -
> look at the usdct web site for how NOT to do it. My personal bet is that
> these strokes have french fried lungs after each dive based on the farm
> animility with which they are conducting the deco. The correct intervals
> are also far different from what these amateurs are doing.
>
> John E. Ivanic NACD#1648 wrote:
> >
> > I was just reading the latest edition of deep tech, and read the article
> > on the boy's that were diving in merimac cave system.
> > One of the fellows said he used 20/20 trimix for break gas, I was
> > wondering what the advantages or disadvantages are. I understand that a
> > lower O2% would be good, but what about the 20% He?
> >
> > John Ivanic comments: ivanic@di*.ne*
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