Charlie99:
How does the rule of thirds help when your tank O-ring blows or you have catastrophic no-gas failure of your reg at 100+', no redundant gas source, and no buddy around?
Thanks for the input. I have never heard of a "no-gas failure" of a regulator unless the tank is empty. Then it's really not a regulator problem, it's operator error, poor planning, failure to pay attention, etc. Having been factory trained by Zeagle and Sherwood Scuba I know a thing or two about regs. (at least thiers). If something goes wrong, LP seat bursts, O-ring goes out, etc...the reguator will free flow like crazy. This is a safety feature inherent in almost all regulators.
So, let's say that we are at 120ft, we have 2000psi left in our tank, and BAM! our reg begins to free flow due to some type of problem. If we go back to our OW training (at least PADI) we are taught how to breathe from a free flowing regulator. And since ScubaMike dives by the rule of 3rds, he knows that at 2000psi it's time to end the dive anyway.
So even with a free flowing reg, or a tank valve leaking like crazy, you've got 2000 pounds of air to get you to the surface. If it's a tank O-Ring I would do the following:
1. Stay cool and don't panic.
2. Take off my BC and hold it in front of me.
3. Keep a close eye on my bouancy.
4. Close the tank valve until the stream of bubbles is smaller
5. Breathe those bubbles from the tank valve much like that of a free-flowing reg.
6. Safely make my ascent, keeping an eye on my air pressue.
7. If I've got enough air at 30-15 feet or so, then do my safety stop.
People who dive thier tanks down to 750-500psi and then end the dive won't be able to do this and will have serious problems should something happen. Also, even with a redundant gas source, a failure of any piece of equipment means the dive is over!
Here's something to think about...what if your backup reg (which never get's used) or your backup gas (which has had the same 3000 psi in it for 3 years) fails?
All I am saying is that no matter how safe we dive, things can and do happen. Granted, a redundant air source and a buddy could be of help in a bad situation. But they both could also cause a lot of problems or give you a false sense of security that over-rides common sense and safe diving skills.
Thanks for your comments and questions...discussions like this that make us think also make us better divers in the long run.
Mike Rushton