Posted by northcoast diver on February 24, 2005 at 16:38:44:
In Reply to: Re: take any advice that you want posted by Chuck Tribolet on February 23, 2005 at 19:12:55:
If you are diving steel 72 single tank(s) with EAN36 and more than 1 hour surface intervals, and abiding by the 1.4 ppO2 limitations, then you are breathing a perfect mix, in a perfect tank size, for your average air consumption rate.
And you should be able to dive as many dives in a day with this configuration and this surface interval as you want. And you would virtually never need to refer to your dive computer's built in NDL algorithm.
Virtually at any depth you are diving, your tank will work for you to limit your dive time to say well within the scientifically known NDL times.
That is because your EAD will be shallower than 65 ft at virtually all times. And the volume of gas in your tank would be only enough to let you dive within those NDL times.
It is a perfect configuration.
If your tanks are bigger, such as 80s or 95s or 100s or 120s, that is only when you could push up against the NDLs. Even with 80s I believe you would be fine, as long as you kept a safe reserve. That also suggests that people choosing larger than 72 or 80 cu ft tanks need to beware.
That is the beauty of selecting the "best mix," together with the best tank size including reserves, for your planned dive. It is an optimization of dive planning.
Before the advent of Nitrox, this was not possible all the way to 100 ft. Nitrox makes it possible.
As for your pretty girlfriend, the same applies to her, when she is buddied with you on a dive with the same tanks, because she is going to go up when you go up. She would need smaller 65s or 55s for it to work for her on her own with another female diver of the same size as she.
The concept fails when people foolishly choose larger sized single tanks, or else non-ideal gas mixes for their diving depth.
Air is a great mix to 65 ft.
EAN36 or 35 is best for diving from 70 to 100 ft.
For virtually risk free diving, these are the mixes that are ideal.
You yourself prove it every time you go diving with EAN36 in your boat. And your own personal excellent history of DCI-symptom free diving validates it as well.
Would I recommend this type of configuration and gas mix selections to everyone? If trained on EANx then YES. If not trained on EANx, then I would highly recommend they limit their depth on air to 65 ft. That is, if they want virtually DCI-risk free diving.
That simplifies things immensely. No more dive computers nor NDL tables needed. Just care-free scuba diving performed with ideal choices of gear and breathing mix.
I do not have much time to teach anymore. It was fun while it lasted from 2002 to 2004. My last corporate promotion has taken virtually all of my free time away.
I know few people who teach for the money. We teach for the pleasure of teaching, and to support our various training agencies. Everyone whom I taught, I gave them the 65 ft principle, and a basic understanding of nitrox. If they are diving deeper than 65 feet on air and they were taught by me, then they are forgetting what I taught them about ideal mixes for various depths. My chart went all the way to 400 ft and below (the range of professional oil-rig divers and Navy salvage teams).