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View Full Version : A good tip in a book I read.



moosicman
03-08-2008, 11:03
Has anyone ever read the book by Peter Benchley called "Shark Life"? It is a quick read and I found a great tip for divers in it. He was recanting a story of a dive he was on in which he wasn't paying attention and emptied his tank. So he gives the OOA signal to his buddy but his buddy can't get to him right away for reasons of a large shark or two, so he has to ascend. By ascending, what little was left of the air in the tank expanded and gave him a puff or two which got him close enough to the surface to do an CESA.

Suprisingly, I had never heard of that before, though it stands to reason I suppose, and I thought it might be something to share with you.

The book is a good one too. I would recommend it, although alot of it is elementary.

NitroWill
03-08-2008, 11:15
This is why you should keep your regulator in your mouth if you are forced into an emergency ascent. I thought this was covered in most OW classes, but I guess not all. It's good to remember - but nothing that watching your air and diving your plan won't prevent

Splitlip
03-08-2008, 12:05
Boyle's Law, n'est pas?

Will:
When I recieved my NAUI OW cert in the 70's it was discussed at length. I took an AOW in 1999 to tune up. Never discussed.

My daughter was just certified in 2007. To the best of my knowledge, although Boyles law was studied, the specifics of this were not made clear.

But then in my open water class, we also were shown how to breath off a tank without a regulator :), and how to buddy breath lol. No octos and no BC's either. Fact is though, our buoyancy skills were spot on!

EDIT:
I stand corrected. I just spoke to my daughter. in her PADI OW she did learn that the air in the tank will expand as she gets higher in the water column and she can get air from an "empty" tank (at depth).

Another EDIT: Just spoke to my cousin from Key West. Recently NAUI OW certified. Does not recall learning to sip the reg.

jeepbrew
03-08-2008, 12:18
But then in my open water class, we also were shown how to breath off a tank without a regulator :)

When I originally got certified at the old age of 12 (1993), we did not do this... however, when I took a refresher (at the same time my g/f got OW certified) in 2006, we had to act as if we had a 1st stage failure, remove the BC, remove regs from tank, and breath off the tank for several minutes. Well, I guess we didn't HAVE to do it, but everyone in the class did.

newways
03-08-2008, 12:40
It was covered in my OW, AOW, and scuba tuneup through PADI.

Chocoholic
03-08-2008, 13:25
It was covered in my Naui class long ago, but I never got to breathe off the tank:smiley19:

Splitlip
03-08-2008, 13:40
But then in my open water class, we also were shown how to breath off a tank without a regulator :)

When I originally got certified at the old age of 12 (1993), we did not do this... however, when I took a refresher (at the same time my g/f got OW certified) in 2006, we had to act as if we had a 1st stage failure, remove the BC, remove regs from tank, and breath off the tank for several minutes. Well, I guess we didn't HAVE to do it, but everyone in the class did.

cool. What agency?

mitchy
03-08-2008, 14:01
We learned that in our OW last year (PADI). We were told numerous times about the availability of a few breathes being available during CESA assent.

jeepbrew
03-08-2008, 14:46
But then in my open water class, we also were shown how to breath off a tank without a regulator :)

When I originally got certified at the old age of 12 (1993), we did not do this... however, when I took a refresher (at the same time my g/f got OW certified) in 2006, we had to act as if we had a 1st stage failure, remove the BC, remove regs from tank, and breath off the tank for several minutes. Well, I guess we didn't HAVE to do it, but everyone in the class did.

cool. What agency?

PADI, but the instructor didn't just teach the basics. She covered much more than required. I was already an experienced diver so I knew most of it, but it was a great learning experience to my g/f who was a newbie!

Splitlip
03-08-2008, 14:52
I think a lot depends on the instructor.

cummings66
03-08-2008, 15:29
I was told this in my Padi OW course, nothing mentioned about it later though.

Defman
03-08-2008, 16:06
I thought this was covered in most OW classes, but I guess not all.

It was covered in mine. This might be a good example of the instructor making the difference and not the agency. Not bagging on the original poster's instructor, just a generalized comment.

CaptainRon
03-08-2008, 16:40
The air in the tank does not actually expand. What happens is that as you ascend, the ambient pressure decreases, thereby allowing the tank pressure to overcome the ambient pressure so air from the tank can escape through the regulator. Example, if you are at 99 ft depth and "run out" of air, there is still actually 4 atmospheres (approx 60 psi) of air in the tank, although your lungs can not expand to draw it out because the ambient pressure on your body is also 4 atmospheres and there is no pressure differential. As you ascend to 66 feet, the ambient pressure on your chest decreases to 3 atmospheres while the pressure in the tank is still at 4 atmospheres. This pressure differential allows your lungs to expand and draw air out of the tank until the differential is again equalized or your lungs are full and the regulator stops the flow of air. So the air inside the tank never actually expands. The pressure on the body just becomes less. Am I making sense?

By the way...I have now officially reached 250 posts....Time to go shopping!!! :smiley31:

reeldive
03-08-2008, 16:56
But then in my open water class, we also were shown how to breath off a tank without a regulator :)

When I originally got certified at the old age of 12 (1993), we did not do this... however, when I took a refresher (at the same time my g/f got OW certified) in 2006, we had to act as if we had a 1st stage failure, remove the BC, remove regs from tank, and breath off the tank for several minutes. Well, I guess we didn't HAVE to do it, but everyone in the class did.
Kinda hard on the reg don't you think?

immediate overhaul required!!!

Splitlip
03-08-2008, 17:35
But then in my open water class, we also were shown how to breath off a tank without a regulator :)

When I originally got certified at the old age of 12 (1993), we did not do this... however, when I took a refresher (at the same time my g/f got OW certified) in 2006, we had to act as if we had a 1st stage failure, remove the BC, remove regs from tank, and breath off the tank for several minutes. Well, I guess we didn't HAVE to do it, but everyone in the class did.
Kinda hard on the reg don't you think?

immediate overhaul required!!!

Only if you repressurize. Even then it is really the SPG which is at risk.
Good point though.
I assume it was done in a pool where the students could just stand up after the drill.


After the drill, they would remove the the high pressure hose, reattach the 1st stage and blow any water out the HP port and purge the 2nd stage.

cummings66
03-08-2008, 18:09
It's my understanding that doing this in the pool in that manner isn't really hard on the gear, essentially it's like you took it apart and flushed the dirt out with water.

Not saying you can borrow my regs and do it, I might smack you if you tried it.

Athena2c
03-08-2008, 18:11
This was covered in my NAUI OW class in 2004, but not my PADI AOW class in 2005

moosicman
03-08-2008, 20:58
I am thinking that some of this stuff, though important as anything else, is like any other class would be: some instructors emphasize and stress different aspects. Of course, Boyle's Law was extensively covered in my OW cert, but of course we didn't discuss at length EVERY ramification that this may possibly have or that we could possibly incur while on a dive. For that I imagine I would still be in training, as would we all. This, to me, seems to be a specific advantage that is realized from the general idea of Boyle's Law, as there are other tips and tricks. This particular trick was not covered in my OW but I know from discussing my cert. and training at length with others on this forum that my instructor was top notch in comparison to the norm of what is out there. It just is a variant with this particular instructor that he didn't mention this. He did, more than likely, cover other tips and advice that perhaps weren't covered in someone else's class. :)