Jim

I understand and agree with the sentiment.  However, a balance is needed.  It
is generally safer to avoid the deco in the first place than to incur it and
require a deco gas off gas effectively.  So many people are trained by the
agencies that you can dive air and deco on 80% *for safety*.  This is
absolute BS.  Better to use an appropriate O2 content in the bottom gas and
avoid the deco penalty altogether. 

Mostly the reason people give for not doing this is one of cost - having to
O2 clean (and keep clean) their back gas cylinders, whereas a stage is
dedicated to the gas.

David Shimell
shimell@se*.co* <mailto:shimell@se*.co*> 
DDI: 01932 814096 * Mobile: 07770 282 202 * Fax: 01932 814343
Project Manager, IBM UK Web Server Group, Sequent Computer Systems Ltd,
Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF, UK
registered in England and Wales under company number: 1999363, registered
office as above

-----Original Message-----
From:	Jim Cobb [SMTP:cobber@ci*.co*]
Sent:	Monday, October 09, 2000 7:55 PM
To:	dmdalton
Cc:	dwiden@ho*.co*; donburke56@ne*.ne*; 'Paul Braunbehrens';
techdiver@aquanaut.com
Subject:	Re: rec trimix

I know this is going to piss off a lot of rec divers but I believe that
increasing your bottom PP02's for the purpose of avoiding a deco obligation
is a really stupid idea. It is typical of our sport that this principle is
embraced by almost everybody. Even to the point of calling potentially deadly
hyperoxic mixes "safeair". 

I think there should be an industry-wide ban of bottom or working PP02's of
anything over 1.2. And if you need to spend more time down there then you
need to do it right with doubles and a deco plan. The idea of "standard"
trimixes with 02 of 32 or 36 or greater is inverse to common sense. 

   Jim 

On Monday, October 9, 2000, at 01:20 AM, dmdalton wrote: 

David, Don & whomever else, 

Why does this need to be a gas that "tracks" air? Anyone who would be 
interested in the minimal extra training necessary for a recreationally 
oriented Trimix would either already be Nitrox trained or certainly capable 
of it. As was already pointed out a Tri-Ox course could easily make Nitrox a 
thing of the past. If we are talking about "no stop dives" then wouldn't it 
make sense to boost the O2 level to get some increased bottom time? A 21X24 
@ 130 ft for 5 minutes calls for 1 min at 30, 20 & 10 (Deco Planner GF - lo 
25/hi 90). While a 28 X 35 gives you 10 min @ 130 and only adds 1 min at 40 
ft to the above. Nitrox has it's limits and so would Tri-Ox. I would venture 
to say that an individual breathing Tri-Ox of 28 X 35 would be far less 
likely to ignore the 130 ft limit than someone breathing EAN 28. 

As for the Rec Agencies, I think they will be the ones to embrace this mix 
which would be one more specialty that they could get into their curriculum. 
They certainly have all embraced devil gas, I'm sorry, Nitrox. Yeah, I know 
it took a while but when Tri-Ox hit's for real they will all jump on it like 
a chicken on a June bug.  The gentleman I took Nitrox from ( a former NOAA 
Nitrox Diver of 14 years) was talking about standardized Tri-Ox 32 & Tri-Ox 
36, 3 years ago when I took the course. 

I believe the bigger challenge is the few shops that pump Trimix. In the DC 
area I know of only one shop that pumps it and I understand that they are 
getting in the neighborhood of $80 for a single tank of Trimix. Outlandish, 
but then I understand that in NY you can get hit up $20 for a single of 
Nitrox. 

Dave Dalton 


----- Original Message ----- 
From: David B. Widen <dwiden@ho*.co*> 
To: <donburke56@ne*.ne*>; 'Paul Braunbehrens' <Bakalite@ba*.co*>; 
<techdiver@aquanaut.com> 
Sent: Sunday, October 08, 2000 2:53 PM 
Subject: RE: rec trimix 


> Don 
> 
> Good thought. It will be hell to get the rec agency to support. 
> I ran some of the numbers through Deco Planner and some other 
calculations. 
> 
> To more closely track air and without penalties a 21x24 works with END of 
80 
> IAW DecoPlanner and END of 90 if you calc with N2 & O2 as narcotic gases. 
> Without building the whole tables w/SIT and repet groups. There are 
several 
> general mixes that would work well. The Normoxic value would serve the 
> uninformed or hard headed person who exceeds 130. It would also support 
and 
> assist in the transistion of new divers to this type of dive gas and idea. 
> 
> Type Cost: 21x24 $.215/cuft  21x30 $.252/cuft 
> AL80 21x24 ~$17   21x30 ~$20 
> ST95 21x24 ~$21   21x30 ~$24 
> 
> Cost increase 3 to 5 times without over fills. 
> 
> David 
> 
> > -----Original Message----- 
> > From: Don Burke [mailto:donburke56@ya*.co*] 
> > Sent: Sunday, October 08, 2000 7:56 AM 
> > To: Paul Braunbehrens; techdiver@aquanaut.com 
> > Subject: Re:rec trimix 
> > 
> > 
> > Comments scattered within 
> > 
> > --- Paul Braunbehrens <Bakalite@ba*.co*> wrote: 
> > > I think that this is where trimix computers come in. 
> > >  Even if it's a 
> > > good "drop in" gas, I'd still like to track what I'm 
> > > really using. 
> > 
> > Certainly.  It isn't rocket science in any case.  I 
> > haven't worked out _every_ possibility so the He 
> > content may have to be backed off a couple of points 
> > to stay inside the air tables. 
> > 
> > A set of rec-tri tables wouldn't seem to be too hard 
> > to make up for repetitive diving, although PADI would 
> > probably have to actually come up with a new set of 
> > surface interval numbers to allow for He instead of 
> > the Xerox solution used for the surface intervals on 
> > the PADI EAN tables. 
> > 
> > 
> > > Also, because of O2 Tox there would have to be some 
> > > kind of an 
> > > "orientation class" at the least.  If you go down to 
> > > 160 on air and 
> > > come back up right away you're stupid, but you won't 
> > > tox on O2.  A 
> > > "drop in" gas would need some serious warning if it 
> > > has a higher O2 
> > > content. 
> > 
> > Yeah, the orientation would be: 
> > 
> > "Remember when I told you to stay shallower than 130? 
> > Well this time I mean it." 
> > 
> > You didn't mention the CNS clock, but since we are on 
> > the subject of O2, I haven't figured out a way to run 
> > out the clock with 28% O2 without going well into deco 
> > stop diving or going below 130.  I doubt there is one. 
> > 
> > > Don Burke wrote: 
> > > ~ 
> > > >As variation on the same theme, how about 28/35 as 
> > > a "drop-in" replacement for air? 
> > > > 
> > > >It is good to 130 feet under any conditions a rec 
> > > diver will see. 
> > > > 
> > > >The no stop times are longer than for air. 
> > > > 
> > > >The END at 130 feet is about 80 feet. 
> > > > 
> > > >The only downside is cost. 
> > > > 
> > > >Don Burke 
> > > >Chesapeake, Virginia 
> > > > 
> 
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