Posted by Karl S. on November 18, 2001 at 17:55:48:
In Reply to: Re: I completely agree that NitrOx is a better mix than air for scuba posted by George Austin on November 18, 2001 at 16:50:03:
George, you mentioned "deep air." I did some deep air diving earlier this year. I have since become NitrOx certified, and also Advanced NitrOx certified, and am in the final stages of Stage Deco training, and so I have no need to dive deep on air anymore, and I would not go deeper than ... 25 fsw! ... on air ever again.
More specifically, I now avoid air as a diving mix altogether. Live and learn. I lived. I learned. God blessed me this time.
The TDI instructor whom I am now working with for TDI certification, towards the ultimate objective of TriMix certification, has our class diving to 150 fsw on EAN25. The END of EAN25 at 150 fsw as you know equals [ 0.75/0.79 x (150 + 33) - 33] = 141 which does not look like a huge difference. However, for me, there seems to be a huge threshhold at END 145 fsw for narcosis, and so EAN25 seems to be a huge benefit for me at least over air when diving to 150 fsw on technical deco dives.
Our class has a few more dives to 150 fsw on EAN25, after which we will begin the norm-oxic phase of TDI TriMix training. After certifying for TriMix, I do not plan to go deeper than 110 fsw on any gas besides TriMix ever again. At that point, there would simply be no need for me to do it.
110 fsw is as you know the MOD at 1.4 PO2 of EAN32, the gas mix that I do most all of my recreational diving on. Here on the West Coast, as you know, we are encouraged to set our MOD based on a PO2 of 1.4 since the water is very cold. An MOD based on a PO2 of 1.6 would be perfectly acceptible if the water was warmer here and the workload was comparatively light at depth, such as floating around inflating and deflating your B/C with only light fin kicking.
Im throwing all these basic consideration in just in case someone new is reading this, and so that divers whom I respect, like KevinR & JeffB wont feel like they have to flame me over it.
So much for deep air, and even deep NitrOx. I hope it doesnt come up again.
Mike Kane was one of the divers who encouraged me to move towards TriMix if I felt there was a particular reason why I should be diving deeper than 100 fsw, and he/they were right about that, and I appreciate him and the other guy, IanP, a NorCal diver, for stearing me in that direction.
These dive boards are certainly good for something, sometimes, even though not everyone is civil to each other all the time, unfortunately.
What should the depth limitation for recreational air diving be? In my opinion, 25 fsw!
Absent that, it seems to me that 100 fsw should be the deepest that any recreational diver ever dives, on any gas mix, air or NitrOx, before become Stage Decompression trained and certified. Realistically speaking, 60 feet is probably a better limit for recreational diving.
I dont know how it got as deep as 130 fsw in the literature. But that seems way too deep for the average Joe and Sally Resort Diver. Most rental gear doesnt even seem safe deeper than about 25 fsw. Most rental regulators dont seem to breathe very well deeper than about 25 fsw. All, in my opinion and within my own limited experience, of course.
Im putting all these personal opinion caveats in so that divers whom I respect, like KevinR and JeffB, wont flame me over them.
What about all the international dive spots that dont offer TriMix nor NitrOx? Well, I am new to exotic international scuba travel, and since ignorance is bliss, I personally would simply choose not to visit a site that does not offer TriMix and/or NitrOx. And if for some reason I changed my mind and did visit, then I would want to limit my depth on air to 25 fsw.
Regarding the economics of NitrOx, which you have pointed out, I personally can see both sides of that issue. On the one hand, I can see YMCA or NAUI or PADI or SSI or IANTD or TDI or GUE or any of the other many diving agencies taking a very futuristic viewpoint and ruling that for their certifications, air as a diving mix is unfit, and only NitrOx would be allowed.
That makes sense, and I could live with that. I believe that GUE has effectively already done that, unless I am mistaken. I am no expert on GUE.
On the other hand, I could also see letting individual divers make up their own minds, and continuing to offer Basic OW1 training as based on air, with NitrOx being considered a follow-up specialty, like it is now. The unfortunate part of that current approach is that the message is not getting out to new divers (nor to some dive store owners in some cases) that air as a diving mix has its major drawbacks.
Pool training is the only time that it seems to me that air as a diving mix is completely OK, in addition to scrubbing the bottom of someone's yacht with scuba gear on.
The nice thing about the recreational NitrOx course is that you can learn it all in one night, since it is table based. Advanced NitrOx is primarily formula driven, and it took me several weeks of study before I could master all the formulae related to Advanced NitrOx. So I agree with you there too, that both courses satisfy the various needs of developing divers.
I know of some dive stores that still do not offer NitrOx fills. I personally hope that soon, all dive stores will offer it. I have close friends who own dive stores who dont offer NitrOx. I respect them. So I wont put them down for their personal preference to go with air at their store rather than NitrOx.
My view is that in a perfect world, all scuba stores would offer everyone a choice of air, NitrOx, or TriMix, AND have booster pumps to fill all tanks and deco bottles and DAN O2 kits to up to 3600 psi as appropriate of the selected gas.
How many centuries do you think it will be before that day happens???
Best regards,
/s/ Karl S.
PADI D/M
TDI Advanced Nitrox