Posted by MHK on October 09, 2000 at 16:39:18:
In Reply to: Rec Trimix (Triox) posted by Jim Hoffmann on October 09, 2000 at 16:18:43:
Jim,
I think much of the reason that trimix isn't as popular as it should be has a couple of valid reasons:
1) Of course, cost concerns;
2) Lack of availablilty ( as far as I know you are the only shop that carries it anywhere in the South Bay );
3) Need for additional training;
All the above being said, I couldn't agree with you more...
The level of misinformation about Helium is freightening. The misconception about Helium ( He ) is tantamount to the assault Nitrox withstood years ago. While some still believe that Nitrox is death gas, most reasonable people have moved on from that debate.
My sense is the more information given out about He the better.
He, is a much *friendlier* gas than Nitrogen ( N2), dives in the 100' - 200' range should always be done with some He in the mix, the decompression uptake is NEARLY identical to the profiles using the standard Buhlman algorithms.
I just spoke last week at the Sea Diver's Dive Club about this very subject. He is a very misunderstood medium. Whenever I mention the word trimix to anyone the vision of double tanks, deco gases and 300' dives immediately pops into everyones head. But the fact of the matter, while for sure He is used in the deep stuff, it also has VERY useful applications to the dives in the 100' - 200' range.
I have had this discussion many times with diver's and I hear often * I have been diving to 180' ( or whatever ) for so long now and I can dive deep on air.... The fact of the matter is that you can learn to dive deep on air, you don't grow out of narcosis and you are safer diving a triox to 180' than you are on air.. I also hear often that recreational limits provide for 130' max...
My very clear and strong message is that we ABSOLUTELY know that diver's are diving deeper than 130', go on 99% of the charters to the oil rigs, to Farnsworth, Osborne, Moody, Palawaan, to name a few. On all these charter's you have a few diver's that go down deeper than 130'..
My question then is, who is safer someone going to 180' on air, or someone who is diving a 22/30???
A 22/30 means 22% Oxygen 30 Helium and 48% Nitrogen.. This will yield a END ( Equivalent Narcotic Depth ) of 96' and a P02 of 1.4.. Meaning you are at 180' but you have the clear head as if you were at 96'. Using a 1.6 you could have an MOD of 207' so there is plenty of room to avoid oxygen toxicity.. ( Note, I recomend using a P02 of 1.4)..
It seems to me that dives in the 100' - 200' range are done much safer using Triox. Dives such as the Moody, Fransworth, Oil Rigs, Osborne all can be done safer withing *basically* the same dive profiles that are currently being used. I would note that you should incorporate deep stops into your profile but other than that, the profiles are pretty close...
I hope that some of the misinformation get's corrected in this thread and this could be a very useful thread for our community.
Thanks Jim for bringing it up...
Later