Decompression Theory

[Dr Deco]

Dear Readers:

As you have noted in the past, I only comment on topics related to decompression physiology, since my personal experience ends there.

This deep air and solo diving sounds dangerous to me. I personally enjoy the interchange of the readers on the FORUM.

Dr Deco

 

[Liquid]

Doc,
I belive everyone here feels the same as you. I dont remeber how we got to this issue, but from the responses, everyone here is against deep air and solo divings.

LY-

I must agree with you on everything you said.
who exactlyis this tom?

I read the link you gave, could hardly understand it (really bad language). It seems to me that part of the argument there is true. Diving with mixes can be a problem, for people that think they understand what they do. Using several mixes for a dive, that requires a thourogh preparation and planing and has a limited time for every mix and depth, for someone that is not throughly trained, is dangerouse, maibe more than using air.

I do, though, belive that IANTD incourages use of nitrox for dives, if not also trimix, as they make a lot of money of these things!

P.S-
What are your feelings about ANDI?
here in israel they are the largest.

 

[Lost Yooper]

Liquid,

Tom Mount is CEO of the board of directors of IANTD. Bret Gilliam is the founder, president and CEO of TDI.

ANDI requires deep air classes as a prerequisite to trimix. At least IANTD has a "normoxic" trimix class that doesn't require deep air training as a prerequisite (or so I've heard). This is a step in the "right" direction, but they continue to endorse deep air diving. I'm not sure if TDI has followed suit with IANTD or still requires deep air as a prerequisite to trimix. Regardless, all of these agencies endorse deep air and they have no shortage of followers.

The funny thing is, they seem to scare the crap out of everyone by saying mix gas diving is potentially "dangerous" or whatever, then say it's OK after you have deep air training. I don't get it. Trimix isn't rocket science and, IMO, is safer than air or nitrox on virtually every level. I believe these agencies, as well as PADI, NAUI, and everyone else knows this as well, but are afraid of economic reprecussions (as opposed to a safer industry) if they were to change the industry norms. One can learn trimix as quickly as a nitrox class.

Later.

Mike

 

[Diverl]

Thanks for all the info, I really appreciate it. Some of you mentioned you like to fully understand the theory behind whatever you are doing, so do I.

Putting the deep air aside for a moment, how come none of the training agencies except gue offers a decompression course for shallower depths? While going deep does appeal to me, I can think of a few times where a 50 or 60 minute dive at 100 feet would be fantastic (wreck Dive). I like the layout of the gue courses, however I do not know of a training center in Canada. Seattle is probably the closest location, with our exchange rate it becomes really expensive fast.

 

[Liquid]

DIverl,

Training deepr dosent mean you can't do it. It's just simpler, becouse the dives won't be so long. Ofcourse you can make shalower dives, 100 fsw long dives are done regularly, aspecialy with wrecs. you use what you learn in the classes, it's the same tables.

Lost yoopers,

I can't agree with you. I do belive that one should get a more in depth training of decompression using niterox before starting with trimix. In the course, you do not dive to the limit, and are encouraged to go on to trimix. You can't just take someone with no technical background and throw on him the trimix. It's an opening for disasters, aspecialy when he goes diving without instructors and plans his own dives using the tables. It's enough to start with different kinds of niterox mixes for different stages of the dive. Diving up to 50 meters with differnt mixtures of niterox can be fairly safe. at greater depths, when you have to cut even more on the O2 percentage due to O2 poisoning risk, it loses the effect and trimix gets more essential, but up to this depth niterox is good enough.

I know the requirements for both ANDI and IANTD courses are niterox certification. The courses also use differnt mixes in the dives, so makeing "deep air" acusations here may be wrong.

 

[Lost Yooper]

Liquid,

Tell me what nitrox mixture you would use for a 190' dive which is endorsed by ANDI's Extended-Range Exploration Diver course (a prerequisite class for their trimix course). Go to their web site and see for yourself.

We'll have to agree to disagree, but trimix "training" can be conducted the exact same way as an extended range or deco procedures class except you would use trimix back gas instead of air or nitrox. IMO, the only prerequisite that should be required for trimix is Adv. Nitrox (cert. for 100% O2). Deco procedures and trimix can easily be incorporated into one class. How economical, eh! There's just a few extra rules and a bit of physiology that has to be taught to learn trimix. Helium isn't the poison that so many make it out to be.

The way most agencies do it, you have to already be certified in deco procedures and extended range. Then they make you take a trimix course which is a 100% theory based course and make you do actual dives so they can watch you (who might have a 1000 decompression dives under your belt) swim around with trimix on your back -- whoopee!! The swimming doesn't change just because you've added helium to your back mix, just a little theory, physiology, and a change in tables. That's it, and that's why so many people don't bother dishing out $600+ for a trimix course and instead invest that money into their own filling station and go diving -- not that I would do such a thing.

Mike

 

[roakey]

>>...instead invest that money into their own
>>filling station and go diving -- not that I would
>>do such a thing.

OK Mike, theoretically speaking , would you cascade your He or buy a Haskel? I’ve got a two-bottle cascade of O2 and I figure if I put in a three bottle cascade of He (T bottles) I could do He fills for anything but the deepest of dives, which I’m not concerned about at the moment.

By filling the He first I’d “throw away” some O2 if all I was doing was Trimix, but because I won’t give up Nitrox I can still pull the lower O2 bottle down close to zero, so really nothing’s going to be wasted.

Is this what you do (theoretically speaking, of course)?

Roak

 

[Liquid]

ly,

I am to lazy to make the needed claculation for the niterox mixtures, but it is safe (I've done it) enough with niterox.

I'll have to agree about our disagreement. I think that matters should be tought gradualy, and niterox IS simpler than trimix. The reason you are required to do dives in the course is to have you in a supervised enviorment for your first few times. Someone must see that you are working correctly. I don't belive it is different for GUE.

 

[roakey]

Originally posted by Liquid
ly,

I am to lazy to make the needed claculation for the niterox mixtures, but it is safe (I've done it) enough with niterox.

I did the calculation, and without going into details, do you happen to remember what % Nitrox you used on your 190' dive (assuming you kept your O2 dose limited to 1.4 ATA)?

Roak

 

[Lost Yooper]

Ahem! Let me clear my throat, Roakey. Theoretically speaking , I would run a cascade system until I got around to building my own pump for the helium and oxygen. Perhaps a pump that resembles this one... http://www.airspeedpress.com/newbooster.html

Take care Roakey.

Mike