Intentionally out of air (at 15m)

[InTheDrink]

Thanks for the explanation(s).

I get 3.5 breaths with a valve off but the last breath really is a tiny little inconsequential inhale. More of a comfort breath than anything. Makes sense that normal OOA is more gradual and again obvious now you've mentioned it but going below your reg's IP would clearly make the effort essentially in the wrong direction. That's a really useful fact - thanks.

I've had various hard breathing regs in various circumstances, typically getting harder with depth. The first thing I've always done is confirm I wasn't mad last time I read my gauge. I imagine the sensation must be pretty similar?

Cheers,
J

 

[scubafanatic]

Does anyone else not understand what I meant by that, as compared to utilizing expanding gas in the tank on ascent...?

...no sweat, Don...... the NSA decoded it for me within 24 hrs...it's all good !

 

[herman]

Hard breathing regs tend to stay somewhat constant as opposed to the OOA that starts with an almost imperceptible increase in breathing resistance and increases with each breath until there is nothing remaining in the tank. A tank valve that is almost closed will exibit a similar effect at depth and gets worse as you decend due to the density of the air that has to flow through the valve, it will give you a similar feeling. The breath will start off normally but quickly increase in difficulty. The start of each breath will be easy- the hoses have time to fill between breaths but the end of the breath will be difficult because of the pressure drop across the valve. Add some excited breathing on the part of the diver and the problem gets worse quickly and can get dangerous. This is all to common, I watched a DM accidently close off and crack back open a students valve the other day during a predive safety check just before a pool dive. I caught it and no harm but it could have just as easily been on a dive boat and the diver about to make a deep dive, excellent chance of a panicked new diver had that been the case.
An easy way to simulate the last several breaths is to remove the dust cap from a reg and breath off of it with no tank attached. You can get air but it's a lot of work to pull the air through the reg, if your tank is at this stage you had better be close to some air source because you have very few breaths remaining.

 

[da-gd]

Sounds like a lousy DM to me. I love adrenaline and have done some things others might think stupid, but I'd not have agreed to this at 6 dives. Thanks very much for sharing.

 

[cgf]

IHMO it has been a 'good lesson' to OP, anyway DM was there and he would have been ready.
To me it happened during my OWD course with my instructor at my third or fourth dive in the pool, pool of 5 meters deep.
Sure he told me BEFORE he was going to close the valve of cylinder so when it happened I was ready and I did not panic. He said he wanted to make me suddenly recognize I was out of air. I still thank him, the following year it happened, when I did my deep exam, at deco bar the cylinder valve was shutted off. As I tryed to breath, I understood what was going on so, quitely, I took back my mouthpiece to breath normaly again. the DM helping the instructor did not understand what was going on till I showed him there was no air coming out from there...
he (the DM) just shutted of the valve instead of open it.

 

[Uraluni]

I know that's a tech dive procedure, but I've never heard it on recreational.

During a rescue, it's assumed that the diver in trouble will grab for your primary, so it's encouraged to attach your longer, more obvious hose to your primary as that is what will most likely be grasped at in a panic situation.

Just be sure you know where your own octo is.

 

[BioLogic]

I find it interesting that the OP focuses on what the other guy should have done. Perhaps the OP is coming from the perspective of being in DM training now and so is mentally putting himself in the DM's shoes. That's a useful thing to do, absolutely. I just prefer to see the approach of certified divers accepting responsibility for their own behavior, even when light on experience.

I also thought the point was well made that this plan made the new diver unable to be a good buddy if the DM had an issue. If the DM's gauge had been off or some such, both of them would be in a bad situation. Sure you can CESA ... but I sure wouldn't want to, especially after having done enough hard swimming at depth to burn off my whole tank.

 

[Jarred Fedor]

I call BS on all of this. How do you have NAUI Cert with only 4 dives, it should take 8.People putting octos in pockets?! Might as well not have one. Why would you have to fight releasing it anyways, was it glued to the guy? Haiko says he wouldn't dive with that DM I don't believe I would want to dive with you. Try OW again please, for diver's safety.

 

[cdolphin]

I call BS on all of this. How do you have NAUI Cert with only 4 dives, it should take 8.People putting octos in pockets?! Might as well not have one. Why would you have to fight releasing it anyways, was it glued to the guy? Haiko says he wouldn't dive with that DM I don't believe I would want to dive with you. Try OW again please, for diver's safety.

I think he's probably a DM by now, this thread is nine months old....and the dive in the OP was in Feb 09.....no need to "retake" OW.

 

[String]

This shouldn't have happened. With reasonably modern equipment your regulator should have breathed more or less normally until it was showing empty. Like really empty, not 30 bar.

Thats the first thing that caught my eye too. 30-40 bar is still near a quarter full!

Most modern properly serviced regs are designed to drip the IP to ambient + 10 bar or so therefore i wouldnt expect any possible difference in breathing until about 12 bar on the gauge at that depth.

So either the regs didnt work properly, the SPG calibration is wrong or its placebo effect- expecting it to breathe hard so it "did".

I frequently have tanks with 20-50 bar in and there is no noticeable breathing effort change at all.