----- Original Message -----
From: "Carl" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, July 08, 2000 9:25 PM
Subject: Re: [SCUBA-SE] Draeger rebreathers (was:
Re:[SCUBA-SE]DivingDoubles)


> Mike,
>
> > > > > I understand things from Draeger's literature and through speaking
> > with
> > > > > their representatives and Dolphin users, there are still a few
> > negatives.
> > > >
> > > > There are negatives with EVERY rebreather out there.
>
> There are ways to cause problems, just as there are ways to cause
> problems with open circuit.  A loose mouthpiece, a stuck pressure gauge.
>
> > > Ok, give me the negatives that are life threatening on the Halcyon.
> >
> > It's a rebreather.
>
> That is *not* a sufficient answer and I suspect you KNOW that it's not.
> Just say "I don't know of any".

You are right. I did say below that I don't know of any.

>
> > Seriously, I don't know what they are. I have not spent a lot of time
> > studying the Halcyon because it's not likely that I'll win the lottery
and
> > be able to afford one anytime in the very near future. I have no doubt
that
> > it is considerably safer to dive than the Dolphin, but I also have no
doubt
> > that there are ways to kill yourself just as dead with one.
>
> WHAT!!!  UNACCEPTABLE.  If you have NO DOUBT then you must KNOW of AT
> LEAST
> one way to do this, yet, you freely admit that you do NOT know the
> Halcyon
> and therefore are unable to say anything about it.


>
> Sorry for hammering you on this Mike, but either you KNOW something or
> you DO NOT.  You cannot say "I don't know about it BUT I DO KNOW that
> it has death modes similar to others".
>
> > > > You are betting your life on your O2 analyzer for any gas dive, be
it
> > open
> > > > or closed circuit.
> > >
> > > What?!  If I do an OC gas dive the O2 analyzer is *NOT* used in a life
> > > support manner.
> >
> > It most certainly is if you analyze your gas prior to your dive, and I
know
> > that you do that. You are betting your life on that analyser and the O2
cell
> > in it.
>
> No.  You have it absolutely, 100% wrong.  My *primary* way of setting up
> that
> O2 is by determining HOW MUCH PRESSURE O2 I must add to that bottle,
> then
> decanting it, checking the pressure gauge (which I have been watching go
> up).
> I then put in the He (if it's a mix dive - watching the pressure there
> up to
> my predetermined limit), and top off with air to my predetermined limit.
>
> At that point I *KNOW* what gas is in there.  My O2 measuring system is
> used
> ONLY as a backup.  If you doubt what I say here I suggest you go say/ask
> the same question/statment over on cavers or quest and see what response
> you get.
>
> > >I *mix* the gas and I already *KNOW* what percentage
> > > the O2 is.
> >
> > You *KNOW* what % it is if you didn't fuck up the blend.
>
> You are correct.  The point is that I will ONLY get a bad mix *IF AND
> ONLY
> IF* 6 things happen (5 things for a nitrox dive).
>
> 1) I screw up the mix and
> 2) the O2 gauge is off.
> 3) That O2 gauge is reading *exactly* what I expected after I pump Pure
> O2.
> 4) That O2 gauge is reading *exactly* what I expected after I pump He
>    (this one is ONLY for a mix dive).
> 5) That O2 gauge is reading *exactly* what I expected after I pump Air.
> 6) That O2 gauge reads 0 (close to it) when I seal off the chamber with
> the
>    O2 cell in it.  YOu can see the O2 percentage declining - a smaller
> chamber
>    will cause it to go down faster.
>
> Normally the analyzer is stored with the analyzer cell sealed.  When you
> turn
> it on you can take the "0" measurement.  Open up to air to do 20.9%
> measurement.  Check out on 100% O2 to check that.  Those are 3 points
> that you
> *KNOW*.  Tell me, what are the chances of a failed unit working on those
> 3 points?
>
> Oh, I forgot to tell you, I can test the O2 percentage THREE TIMES when
> making
> mix.  First after the O2 is pumped (just to make sure I'm measuring 100%
> O2
> and that the analyzer can see it!).  The second one is after the He is
> pumped
> and finally after the Air is pumped.
>
> Do you know the failure modes of O2 measuring systems?  Can you tell me
> just how many of them would have the O2 gauge be faulty, but, read
> exactly
> what I expectn in 2 (or 3) of the measurement steps above and what the
> PROBABILITY
> of that happening is?
>
> Personally I cannot even conjure up a failure mode that would have the
> meter
> working under the initial conditions I set forth yet still read the
> correct
> values later, can you???
>
> Come on Mike, simply admit you are wrong here.

Ok, I'm wrong.... :-)

And I'm done with it.

Mike