Is that two to three hours dive to > 250fsw BOTTOM TIME?  Remember, Will,
bottom time does not include gearing up or cigarette breaks.

----------
> From: William M. Smithers <will@tr*.co*>
> To: CHKBOONE@ao*.co*; techdiver@aquanaut.com
> Subject: Re: Helium Deco / Wil
> Date: Thursday, July 23, 1998 9:14 PM
> 
> 
> On Thu, 23 Jul 1998, William M. Smithers wrote:
> 
> > Incidentally, that's also why Heliox is a much safer gas
> > for repetetive multi-day diving - it clear almost completely
> > out of your system overnight, unlike N2, which takes
> > 36 hours or so.
> 
> BTW, for this and several other good reasons, I've been 
> diving with NO nitrogen anywhere in the bottom
> and deco mixes for about seven months now - I dive
> Heliox10 end-to-end, with pure O2 for deco starting
> at 20ft.  And I feel *great* after the dives.  Unless
> I'm cruising a reef at 80fsw on Nitrox with an AL80, it's the devil
> gas for me.
> 
> The extra hang time is shorter than you'd think.
> Compared to an appropriate trimix, you're typically looking 
> at an extra 10 minutes or so for an hour-long deco.
> 
> Of course, diving heliox can start to get more than a bit
> pricey, unless you're on a closed circuit rebreather. ;)
> (I typically burn through all of four cubic feet of
> heliox for a typical two or three hour dive to > 250fsw).
> 
> Regards,
> 
> -Will
> 
> 
>  
> >  
> > >     Regardless of the rates of diffusion of two different gasses such
as He
> > > and N2, given a fixed period of time for on-gassing and a symmetrical
cycle
> > > each gas should off-gas completely in the same period of time. 
> > >     If at the same time you pore red marbles into a bucket at a rate
of 50 per
> > > second and blue marbles into the same bucket at a rate of 100 per
second for
> > > 10 seconds then pore them out at the same rates for 10 seconds the
bucket
> > > should be empty of both groups of marbles at the same moment. 
> > >     If, however, they are each pored in at different rates that
decrease
> > > exponentially and then out at linear rates (or close on both counts)
then
> > > there can be a divergence of the points in time at which each is
totally clear
> > > of the bucket.
> > >     This would be true of all tissues, not just the slow ones, and
this is
> > > what I suspect is happening but I am looking for confirmation and a
more
> > > thorough description of the process.     I am not sure that the
exponential /
> > > linear model is valid or uniformly applicable.  
> > > 
> > >     I can see possible merrit in your suggestion if helium diffuses
to points
> > > beyond the influence of the blood stream but this would seem to make
the
> > > process dangerously unpredictable.    I agree that the use of helium
would
> > > probably shift the controlling tissue to a slower one for a portion
of the
> > > dive.
> > >    Actually you are making two dives and two decompressions when
using trimix
> > > and I suspect that the procedures we customarily use are not the most
> > > effective way to manage them.    I suspect that we are making a
descending
> > > excursion on nitrogen at the first gas switch so that we can blow off
helium
> > > earlier in the deco schedule than may be necessary.
> > >     Something like this may be behind George's insistance that 50/50
is a
> > > better deco mix than 36 - because it delays that descending excursion
on
> > > nitrogen rather than jumping the helium deco gun and paying for it
throughout
> > > the rest of the deco by having to dump the nitrogen you took on to do
it.    
> > >     I may be way off base but if I can get a few questions cleared up
I might
> > > be able to shorten and improve the effectiveness of my deco
procedures.
> > > This post is the first question.
> > > 
> > >     I appreciate your response, Wil, and I hope that the explanation
turns out
> > > to be as simple as you suggest but I fear that I am in for some big
headaches
> > > over the next few days, especially if I can get Bill Mee, Eric
Maiken, or John
> > > Crea to bite on this.
> > > 
> > >     Does the above seem reasonable or is my brain so fogged with
thinking
> > > about this stuff that I am missing something obvious ?
> > > 
> > > Chuck Boone
> > > 
> > > 
> > > 
> > > --
> > > Send mail for the `techdiver' mailing list to
`techdiver@aquanaut.com'.
> > > Send subscribe/unsubscribe requests to
`techdiver-request@aquanaut.com'.
> > > 
> > 
> > --
> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> > Send subscribe/unsubscribe requests to
`techdiver-request@aquanaut.com'.
> > 
> --
> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]