Jeff i made many many tests with diferent Ean mixtures belive me
100% oxygen on 6 meters does a hell of a lot diference than 50% on all stops.
Plus you can stick with it on board if you screw up thinks.
To be precise i tested 40% on all deco stops and create an excel table someware
ill try to find it for you but from my personal experience is that nothing
compares
to pure oxygen.

Jeffrey Swann wrote:

> Dear  List,
> George
> Are you saying, that you get into deco time with a single tank.
> This seems to throw away your teachings.
> I mean, frankly where does recreational and tech diving separate.
> I do alot of nitrox type diving.
> That is 20 to 30 m wrecks, multilevel, etc.
> I use a harness routinely now and practice redundancy.
> This brings me to the point:
> What is wrong with carrying  a pony with a single.
> I sling it across my waist, clipped up tight.
> Reg clipped off, on the harness.
> Back gas EAN 36.
> Pony 25 cu ft EAN 50. (or similar)
> Also, if you do a 25 to 30m dive, George are you just using nitrox, or are
> you putting some He in that as well.
> The dive boats we are using for harbour dives, don't lend themselves to
> using twins.
> Excepting if I use my twin 55's.
> Sorry if I am ranting.
> Anybodys comments welcomed!!!
> Jeff of Darwin.
>
> At 20:09 10/01/00 -0500, you wrote:
> >Art, I was kind of thinking that the worse shape you are in , the better
> >that trick would work on a relative basis: the guy who sits on the
> >backgas and extends the stops will ongas more stuff than he loses(
> >although in different places) - his only real chance is to force the gas
> >out and treat himself with the oxygen.
> >
> >For the fit diver, helium especially is a great gas even when the ppo2
> >is low. Bill Me and I deco out on backgas a lot and don't get hit on
> >relativlely deep dives with short bottom times. I hate to admit this,
> >but we do a lot of these on single 80's with no deco gas at all. Now
> >that should get the weenies howling, but see Weinke's stuff - his work
> >says it is very doable.
> >
> >
> >Paltz, Art wrote:
> >>
> >> I've been following this thread with good interest.  Are we saying that on
> >> this particular profile that had we lost the 50/50 mix that we should
> >> probably just follow the planned 50/50 stops but use back gas?  Then do our
> >> planned 100% stops as scheduled?  I think this probably works if you could
> >> just come up to 20 foot anyway.  Knowing that most people are not in the
> >> same shape as George, the question is for the normal diver in relatively
> >> good shape who has done similar dives without having to resort to in-water
> >> contingency planning (i.e. has not lost a gas) and has had no trouble,
> >> should they just follow the planned schedule substituting back gas for
> >> 50/50?  Sorry so long but that's just the way it came out.
> >>
> >> I think to summarize and simplify, if in descent shape and experienced in
> >> these types of dives and you loose the deeper gas should you:
> >> a). Substitute lost gas with previous gas (possibly back gas) and continue
> >> with planned schedule.
> >> b). Do to previous gas (back gas in this instance) and try and fudge a
> >> little by adding stops (probably dangerous on deep stops)
> >> c). Panic and surface, signal for correct gas and try and go down and hold
> >> your nuts hoping someone comes to the rescue.
> >> d). Something else?
> >>
> >> The above assumes that "previous gas" is probably better than just saying
> >> bottom mix.  Correct me if I'm wrong but I would assume that if you were
> >> using say 35% Nitrox, 50/50 and O2 in the schedule you should use the
> >> remaining 35% for the 50/50 stops if you lost the 50/50 gas.  Maybe on a
> >> profile where you're necessitating more than 2 deco gases the answer
> >> changes.
> >>
> >> Thanks,
> >> Art.
> >>
> >>         -----Original Message-----
> >>         From:   kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*]
> >>         Sent:   Monday, January 10, 2000 10:14 AM
> >>         To:     Shimell, David (shimell)
> >>         Cc:     Ian PINKSTONE; techdiver@aquanaut.com
> >>         Subject:        Re: I think I understand
> >>
> >>         Move up = shallower. You can do the 50% as if it were oxygen
> >> timewise,
> >>         and if you lose that you can do the backgas as if it were 50%
> and go
> >> to
> >>         the oxygen. What I am saying is do not extend the table because you
> >> have
> >>         the wrong gas - the upper deco steps can be screwed with
> >> unmercifully
> >>         without any real consiequnces, it is the deep ones that you must so
> >>         corectly.
> >>
> >>         I'll let you in on a little secret - you could do this dive and
> come
> >>         right to 20 in quick steps  , do 20 minues on oxygen and get out
> >> clean -
> >>         done it, and done al ot worse and gotten away with it. These are
> the
> >>         real measures you take in an emergency.
> >>
> >>         Shimell, David (shimell) wrote:
> >>         >
> >>         > George
> >>         >
> >>         > Most interesting stuff...
> >>         >
> >>         > >In real life, you are btter off moving up and taking the
> gradient
> >>         > >offgassing as bubbles while still underwater than you are
> sucking
> >> on the
> >>         > >wrong gas and lengthening the stops,
> >>         >
> >>         > Going pack to your suggested deco profile:
> >>         >
> >>         > Profile 220' FOR 25
> >>         > 16/50, 50% and O2
> >>         >
> >>         > DEPTH   TIME    GAS
> >>         > 160-120 1 MINUTE EACH ON BG
> >>         > 110     1
> >>         > 100     1
> >>         > 090     1
> >>         > 080     1
> >>         > 070     5       50/50
> >>         > 060     2
> >>         > 050     3
> >>         > 040     5
> >>         > 030     8
> >>         > 020     13      OXYGEN
> >>         > 20-0    8
> >>         >
> >>         > I would like to better understand what you mean by "moving up".
> >>         >
> >>         > Following a failure of the 50%, are you suggesting that you
> >> continue the deco
> >>         > as if 50% had been available i.e. follow the schedule but on BG.
> >>         >
> >>         > Or are you saying that 16% is so worthless that you would skip
> the
> >> stops and
> >>         > go straight to O2 at 20', if so what kind of ascent would you do
> >> from 70' to
> >>         > 20' to give your system a chance to cope with the bubbles?
> >>         >
> >>         > David Shimell
> >>         > Email: shimell@se*.co* <mailto:shimell@se*.co*>
> >>         > Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited,
> >>         > 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:   kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*]
> >>         > Sent:   Thursday, January 06, 2000 4:48 PM
> >>         > To:     Ian PINKSTONE
> >>         > Cc:     techdiver@aquanaut.com
> >>         > Subject:        Re: I think I understand
> >>         >
> >>         > Ian, these decos are so severely overstated that a loss of a gas
> >> is
> >>         > insignificant. I did a whole Wakulla deco on my 190 bottle right
> >> through
> >>         > 20 feet on a 30 minute bt at 300 and never got hit, using a
> >> schedule for
> >>         > switching. I kept screwing up the gas switch and not knowing
> it. I
> >> only
> >>         > found out when I got to 20 feet and my O2 was not there, and I
> >> then saw
> >>         > that my 120 and 70 bottle were both untouched, and that I was
> >> about out
> >>         > of gas on my 190 bottle. So much for deco.
> >>         >
> >>         > In real life, you are btter off moving up and taking the gradient
> >>         > offgassing as bubbles while still underwater than you are sucking
> >> on the
> >>         > wrong gas and lengthening the stops, and in real life if you have
> >>         > anything approaching the deocompression time that you are
> >> suggesting
> >>         > here, you not only have support with extra gases available, you
> >> have
> >>         > buddies to share with. I just did a dive wher I shared the 70
> >> bottle
> >>         > with my dive partner last Sunday, and it worked fine.
> >>         >
> >>         > --
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> >>
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