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My usual final stop deco mix is..... - Getting less busy with the fizzy

  • 80/20

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  • 70/30

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  • 50/50

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  • EAN32-40

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  • Air (so I don't have to buy the first round)

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  • I'm on first name terms with the helecopter pilot.

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  • I don't deco dive you insensitive oaf! *sniff*

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This question is a bit like asking...........

"When driving my car, I usually drive at 30mph, 50mph, 70mph, 90mph etc...."

It depends on the circumstances.............

All my diving is with standard gasses. So the answer is......

backgas (32%)
50%
100%

for the sort of diving I do.

Bob
 

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Seeing as the subject is mixed gases....

quick q if anyone can help, rather than start a thread, after PADI nitrox what are the options/agencies that can handle the 40% plus deco training as well as mixed gas diving, say to 100m max depth??

PM's welcom rather than clutter the thread.....

Thanks.

G
 

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[b said:
Quote[/b] (kinetic @ Feb. 27 2004,20:18)]
Let's clutter the thread..........
PM's are too complicated!!

Sounds like you need something like TDI "deco procedures" or IANTD "technical nitrox".  Then, get a bit of experience and do something like IANTD "normoxic trimix" for the mised gas training.

I'm afraid that, in my opinion, most of these courses don't really prepare you for doing these sort of dives properly.  They just give you a ticket which you can use to go and get gas with.

Don't think of it as "training for 40%" or "training for "50%".  Breathing 40% is just as easy as breathing 100%.  You can learn all you need to know in about half an hour, the in-water skills take a little bit longer to master!  and they don't teach them in these classes.

Good luck with the courses anyway.

Bob
 

· Snap Happy
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Jeez 100m is a looong way down.

If you're still on basic nitrox thats a sh*t load of experience you are going to need to build up to do 100m safely.

If you go TDI and you want to do those kinds of dives in the Uk then you need Adv Nitrox and Deco Proc (that'll give you a depth of 45ish m and a ticket to deco on 100%), then a load of dives to build up experience.  Once you've done that do Intro / Basic Trimix which will get you down to 60m (or thereabouts).  Again do a load more dives and move on upto Adv Trimix. A load more dives and then 100m is in your grasp.

As Bob said these courses won't necessarily give you the skills to do 100m safely (esp just deco procedures) but diving with more experienced divers (the kind that can mentor and coach) as you progress, learning, practising and just plain diving will help get you there.

I'm nowhere near this level of diving myself but this is the kind of route I would take.  (although, like Mr Chase, I seem to be getting more interested in, and open to, the DIR way of thinking).

IANTD and PSA(?) all have options to help get you there - as, I guess, would GUE if you are DIR inclined, although I guess you aren't.

HTH, but if not speak to a range of instructors from each of the agencies (in fact if 100m is your goal then do this anyway).  As has been mentioned here before you could certainly do worse than Andy Hayhurst of Dalesdivers who can give you balanced advice and training options.
 

· A short fat well off crap cave diver. Likes wrecks
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Used to use 02 but have gone for 80/20 to get the flexabuility in the shalow stop comitments and to avoid high CNS loadings. Thre is no argument that 100% is the best deco gas but it is not always user freindly.

100m is TDI full trimix. The normal rout is:

Advanced Nitrox
Deco procedures
Entry Level Trimix
Advanced Trimix


OR

Advancd Ntrox
Extended Range
Deco Procedures
Full Trimix

IMHO the first option is the best as Extended Range is basicly a deep air course which is out of date.

As to wether or not the training provided is adiquate depends on the diver and the trianer.

Whilst Andyp and I have bounced 100m and spent a little time at 90m I would say that my deepest proper dive ie: get down there, stay there and come up was 45 @ 65m. I dont think it is dificult to do 100m if you can get your head around the psycological presure of beeing such a long way from home and you have enough He in the mix.  Doing a wreck dive at 100m with penitration or task loading is a whole diferent ball game. Getting caught in a net at 100 and actualy watching your presure gauge drop with each breath and you deco rack up drasticly with every 60seconds down there, is a scarey thaught. I still feel a long way off acheiving that level of dive.

ATB

Mark Chase
 

· Grumbler-chief in Residence
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Got to say, that really is a bit worrying, you look at your guage and think "thats OK, I've got 100 Bar left" as you do this you breath in, and you think "no I haven't".

Next time I am at 100M, I want more gas, got me 15's now, yipee.

Andrew
 

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[b said:
Quote[/b] (Mark Chase @ Feb. 27 2004,22:50)]IMHO the first option is the best as Extended Range is bsicly a deep air course which is out of date.
I'd agree with you there. IMHO diving to 55m on air is asking for trouble and should only really be considered if you have a desperate need for completing an objective at that depth and can't do it trimix for some reason.

I remember seeing "Adventures to the bottom of the sea" on BBC 2 a while back and it had a guy that went to 84m (ish) in air to try and recover a crate which he thought contained gold. He was very lucky he didn't suffer O2 convulsions but seemed genuinely supprised that he lost the use of his hands whilst down there.

No comment....
 

· TDI Instructor Trainer
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[b said:
Quote[/b] (Mark Chase @ Feb. 27 2004,22:50)]100m is TDI full trimix. The normal rout is:

Advanced Nitrox
Deco procedures
Entry Level Trimix
Advanced Trimix
I tend to use either 50% or 80% depending on the circumstances.

I agree with Mark C's comments on the steps to take.

My advice would be to take it slowly and build up your experience. TDI Advanced Nitrox and Deco procedures as a combined course is the best starting point.

After this build on your skills and get confident in to 20-40m range. Then once you have mastered all of these skills move on to Entry trimix to take you past 40m. This is a big step up in terms of depth and skills. Full trimix is a further big step.
 

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[b said:
Quote[/b] (Rob Evans @ Feb. 29 2004,20:27)]Swamp gas eh?  Never knew you could compress methane to 232 bar.  I don't care what the decompression advantages may or not be, I'm not breathing the bastard
Me neither.... although it has been tried:

http://www.techdiver.ws/exotic_gases.shtml

Personally I feel sorry for the poor guy who field tested Radon as a mix gas  
 

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<font color='#000080'>OK, so if O2 is narcotic, which I accept it is, does that mean at deeper stops on high O2 (ie 50% at 22m) I could be more narked than at bottom depth? Or is it going to be very similar narcosis levels? I've not really done the reading on this, any suggestions? Is it possible, if I was diving the optimal mix at depth?
 

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<font color='#000080'>Wouldn't it be better for off-gassing if we used 50/50 heliox instead of 50% nitrox then, too? And cut nitrogen out of the equation? Cost we can leave out as a factor here. If helium is a lighter gas we absorb and get rid of faster, won't this work?
 

· more weaselly than a weaselly thing
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ooooh digsboy, that almost smacks of serious diving ;)

O2 Narcs, I've never bought this one myself. All the data I saw seemed to show it was narcotic at 2bar PO2 and above...

As for using 50/50 for deco. I wouldnt!

Cutting your deco mix with *some* helium is ok, but only if your bottom mix was helium rich. IE try to avoid isobaric counterdiffusion!
 

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[b said:
Quote[/b] (Digger @ Mar. 08 2004,12:37)]Wouldn't it be better for off-gassing if we used 50/50 heliox instead of 50% nitrox then, too? And cut nitrogen out of the equation? Cost we can leave out as a factor here. If helium is a lighter gas we absorb and get rid of faster, won't this work?
<font color='#0000FF'>digger,
the main problem with helium at deco depths is the extra time added to decompression.your best option is to reduce helium as you come shallower and replace that gradually with o2 and nitrogen at depths that the n2 will not be a problem with narcs
or cause a major change in % of gases.
helium is great for a clear head at depth but has no advantage over n2 when shallow and a major factor is the cost of the helium and the run time.
cheers
barrie
 
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