TDI Extended Range - last words of advice?

[tflaris]

Going off to do my combined TDI Adv Nitrox / Deco Procedures / Extended Range course in the Dominican Republic on Sunday.

Any useful last words of advice from the tec veterans on the board?

Stop, Breathe, and Think

 

[battles2a5]

Bull. There's a valid reason 20/80 is used at 1ATA medicinally and there's no "reg" or even water involved.

CO2 increases with work. Air creates more work. Helium lowers WOB as ONE piece of its overall benefit.

Used MEDICINALLY for people with COPD!! In an ambient environment (see my comment on that earlier), not being delivered at pressure from a demand valve to a presumably healthy and fit technical diver.

 

[rjack321]

Used MEDICINALLY for people with COPD!! In an ambient environment (see my comment on that earlier), not being delivered at pressure from a demand valve to a presumably healthy and fit technical diver.

Why do you think that is? Because the DENSITY of air is too much work! Continue to think that gas density is irrelevant if you wish. But even a fit diver can be overwhelmed by high currents and excess work, just like even a marathon runner can burn out on a steep enough hill. There's no good reason to put the odds against you by choosing gear or gases that are known to be more difficult. Are you still using a bleach bottle BC?

 

[DA Aquamaster]

Putting aside all N2 issues... You wouldn't get in the water with a poorly tuned reg, why get in with a poor gas choice making your reg perform marginally?

"Only 20% less dense" is potentially misleading since the WOB is not linear with density.

That is basically crap unless you have a very poorly performing regulator that should not be used with trimix either. I have encountered divers how think a Mk 2 is great at depth (as in 330') with He mixes. That is at best more ehan cancelling any positive benefit you get from the easier flowing trimix.

A decent second stage will flow 65-70 SCFM of air, and the viscosity of air just does not increase that fast until the depths get crazy deep where you are outside the 180' ft range we are discussing. Same with the first stage - any decent first stage suitable for techncial diving will flow 120-150 SCFM minmium and again is more than enough. So that argument really does not wash unless you are diving really cheap and low performing regs. Also, if you look at US Navy tests on regs to 165' you will see regs that perform quite well on air at what is clearly a "deep air" depth.

On the other hand, I often encounter divers who pride themselves on low SAC rates who artificially lower their respiration rate to stretch the most time or penetration out of their third. They are usually quite oblivious to what that will do to their CO2 retention. And ironically these are often the same divers promoting trimix over deep air - with the best of intent as the elevated CO2 level no doubt seriously exacerbates their personal narcosis issues (as well as oxtox risk). What is really bizarre is when one of these divers also preaches about the need for high quality regs and trimix to reduce CO2 retention.

 

[rjack321]

While I don't think its the reg that is much a limiting factor as bronchioles feel free to stack the deck against yourselves, to save money, acclimatize to the buzz, whatever else you use to justify cutting corners. The good thing is you ain't diving with me.

 

[Anti-Hero]

Why would anyone want to dive deep air? I don't need to experience drug addiction to know crack is bad for me. Even the simple helium benefits of reduced WOB, reduced narcosis, and better decompression properties is reason enough to add a fraction.

It just makes sense...

 

[brockbr]

Why would anyone want to dive deep air? I don't need to experience drug addiction to know crack is bad for me. Even the simple helium benefits of reduced WOB, reduced narcosis, and better decompression properties is reason enough to add a fraction.

It just makes sense...

Why deep air? Simple -How about when He isn't available? Think small islands etc.

 

[Anti-Hero]

Why deep air? Simple -How about when He isn't available? Think small islands etc.

Well that's easy for *me* to answer, although my answer certainly will not apply to everyone.

If I am in such a remote location that helium is not available, it's pretty sufficient to say that close and quality medical care is also likely unavailable. Going on that assumption I'd limit all remote island diving to recreational profiles and the use of helium would be moot.

 

[divingbuddy]

If I am in such a remote location that helium is not available, it's pretty sufficient to say that close and quality medical care is also likely unavailable. Going on that assumption I'd limit all remote island diving to recreational profiles and the use of helium would be moot.

I gotta applaud that clear and concise example of common sense (not always as common as I'd like). I always try do the right thing in the right situation and not force the square peg through the round hole.

Deep air? No thanks. Do the dive that your gas choices/equipment/experience/training/teammates/environment/etc. safely permit.

Just my two cents...Cheers!

 

[Bismark]

It's obvious that you two are in no way open to anything outside of your doctrine so I'm not going to argue this anymore. Just out of curiousity through, what kind of experience do you two have diving on air in order to build these arguments? Have you experienced deep air in clear, warm, water and found that you had trouble functioning or are you basing your position purely on anecdotal evidence or your training?

What a waste of time...............