Intentionally out of air (at 15m)

[herman]

In the right circumstances this is actually a good exercise, this particular one was done too deep and not well executed. I do this 2 or 3 times a year, when my tanks need VIS and have to be emptied anyway. When I do it, it is done in very safe, controlled condition, usually in 6ft (2M) of water and a very short distance from shore....basically I can stand up if something goes wrong and my buddy know exactly what is going to happen.
Why do it? To get an accurate feel for how my regs perform in an OOA condition. I never have had it happen "accidently" nor do I anticipate it ever will, I pay carefull attention to my gas but still, I see it as a good exercise. I have seen several post suggesting the turned off valve OOA that is done in some training exercises as an alternative. The 2 are very much different. As an active DM I get the pleasure of demonstrating the valve off procedure fairly often, folks it's not the same. In the valve off drill you get 3 or 4 normal breaths and 1 or 2 harder ones then nothing. A real OOA has a very destinctive "feel" to it and it is well worth experiencing for yourself. Instead of the "just stopped getting air" some report, the reg starts to get a little hard to breath at around 150 psi (10-11 BAR), (the exact value depends on the reg and the depth) and gets progressively harder to breath with each breath. A diver well in tune with his gear can tell something is wrong way before he is truly OOA. You have a good number of breaths before you can no longer get any air out, you can actually suck a good bit of air out of the tank if you try and as you accend you can get a few more breaths.
In the right conditions, this exercise does have a place in training. IMO every diver should experience it on occasion in carefully controlled conditions so they can experience the a more realistic OOA and understand the warning signs the reg give you before it completely stops. If you are in tune with your equipment, it will give you a warning something is wrong way before the event becomes life threating.

Zerbini- if your reg started getting hard to breath at 30-40 bar (435-580 PSI), you need to have your pressure gauge checked. You should not be able to distinguish any difference in breathing until about 10-11 bar (145-159 psi)

 

[InTheDrink]

Herman,
Could you elaborate a little more about the difference between a valve closing drill and real OOA. Seems like you're suggesting usual OOA is slower and has a different feel but if you could please clarify. I close of my valve frequently to see how it feels and I fare, but on the basis that this is similar to how a normal OOG would feel. If you think there's a substantial difference I'd be keen to understand how these differences feel and which is more acute.

Thanks,
John

 

[OnceLoyal]

I agree. About 4 dives ago after about an hour I hung on the line at 15ft. and went down to about 150psi. It started to get hard to breath at 200 for me. I told my DB what I was doing and he hung with me. I felt it was something I should feel and get some experience with.

IMO you were way to deep to screw around like that. I would think the DM would at least want to be in emergency descent depth. I think it is something everyone should experience, just at a safe depth

 

[DandyDon]

Herman,
Could you elaborate a little more about the difference between a valve closing drill and real OOA. Seems like you're suggesting usual OOA is slower and has a different feel but if you could please clarify. I close of my valve frequently to see how it feels and I fare, but on the basis that this is similar to how a normal OOG would feel. If you think there's a substantial difference I'd be keen to understand how these differences feel and which is more acute.

Thanks,
John

If you close your valve at 50 ft down, that's it - finished.

When I ran OOA at 50 ft (dumb mistake, already a thread here), I ascended slowly with tank residual air expanding, paused to take a breath that occurred from the expansion of residual tank gas, ascended slowly to surface, and had enough new air again to inflate my BC and blow my inline dive whistle once.

If you ever screw up likle I did, keep the reg in your mouth. I did that to avoid gasping water, but it gave me a nice breath that I enjoyed. Eh, maybe I should have ascend faster and not run out of expanding lung air exhaling - but it's hard to get that just right the first time, and you hope it's the last.

 

[ONESPEED]

If you close your valve at 50 ft down, that's it - finished.

What the hell does that mean?

 

[DandyDon]

If you close your valve at 50 ft down, that's it - finished.

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

 

[Diver0001]

now that you explained it I do. You had me scratching my head too.

R..

 

[HowardE]

Herman,
Could you elaborate a little more about the difference between a valve closing drill and real OOA. Seems like you're suggesting usual OOA is slower and has a different feel but if you could please clarify. I close of my valve frequently to see how it feels and I fare, but on the basis that this is similar to how a normal OOG would feel. If you think there's a substantial difference I'd be keen to understand how these differences feel and which is more acute.

Thanks,
John

Having tried sucking dry a tank with a smaller 40 cu ft bottle (slung) and having plenty of back gas left...

The difference in a valve turned off vs. organically running out of gas, is

a) that when you're running out of gas in the tank... you can feel it start to get harder to breathe over the period of a few breaths. This should be your "alert, it's getting harder to breathe" and you should be taking action at this point (if you haven't already).

Look at your gauge if you haven't yet (which may be why you're in this mess in the first place)? How much pressure is in the tank? Can you ascend more to allow some expansion in the tank? Signal your buddy. There are plenty of solutions to running low on air.

2) When you turn the tank off... you probably have 2 - 3 breaths in the line (depending on your hose length) -

---

so while the sensation of being out of air can be felt... truly running a tank to empty is an interesting experience, if you are properly prepared for this, which I'm sorry to say... It appears as though the OP was NOT prepared for this, since his buddy was 7 meters (20 feet) away.

Also - I have to question the "OOA" with 400 psi in the tank?? That seems like a lot of gas to be having a hard time breathing? I have to ask... What kind of regulator was it? I know someone mentioned - to not mention it, but that's just not right.

 

[miketsp]

..snip..
I am a very physical person and I enjoy this tough situations, so I agreed. (NOTE: I really was OK with it I wasn't ashamed to say no or anything)

..snip..
I kept a close eye on the air gauge and remmained signaling to him every 10bar drop on the marker. He OKd it and gave me the "keep close" signal.
..snip..
I looked for him, and he was some 7 meters away (a bit to far I might add).
..snip..

03) Too far
He should have kept closer to me, I know he was guiding and it was my responsibility but then again, he could be more careful.
..snip..
Well that's it, please comment and debate.

It's not a bad exercise, when done with someone with more experience, and with the buddy with the gas supply STANDING BY. Allowing that kind of separation from an 8 dive diver who is about to run out of gas is inexcusable, in my book.
..snip..

Just to point out that the major issue here was the separation.
However the OP, by his own admission says he's a very physical person and we all know that newbies tend to race around. I certainly did and I clearly remember being told by DMs on my first 10 dives to "turn off the scooter" .
The OP also stated that he was TOLD to stay close - but didn't. I get the impression that the OP was just head-down intent on burning up air and leaving the DM trailing behind. Not something the DM had planned or expected and was too ashamed afterwards to raise the subject.

..snip..
15m, about 45' more or less, direct accent to the surface after spending how long at what depths? Didn't your instructor tell you that even if you stay with in the limits of the tables you could still take a hit? or with a dive computer.
..snip..

But the intention wasn't to do a CESA at the end of the dive, it was to do an air-shared ascent.

 

[herman]

Herman,
Could you elaborate a little more about the difference between a valve closing drill and real OOA. Seems like you're suggesting usual OOA is slower and has a different feel but if you could please clarify. I close of my valve frequently to see how it feels and I fare, but on the basis that this is similar to how a normal OOG would feel. If you think there's a substantial difference I'd be keen to understand how these differences feel and which is more acute.

Thanks,
John

When your valve is cut off, you get 2 or 3 normal breaths followed by 1 rapidly harder one and then nothing. In a true OOA your regs starts to get progressivley harder breathing after you pass the IP (intermedient pressure) of your reg. The IP is somewhere around 140 psi (about 10 bar) plus a little more depending on depth. The more you draw gas from the tank the harder it gets to breath. As you get near the end of the gas you actually have to suck hard to pull a breath, at the surface it is quite possible to breath from a tank down to just a few psi (less than 1 bar) although you have to work to get the air out. How many breaths depend on the size of the tank but to be honest I have never actually counted the breaths I get.....got to add than to my list for next time. The main thing is it gets harder and harder to breath in a fairly predictable manner as opposed to the couple of breaths, one hard breath and nothing that you get in the valve off drill. If a true OOA was exactly like the valve off drill, you would get 1 "warning" breath as opposed to an actual OOA where you get a good number of progressively harder breaths before you are unable to get any gas at all.

While not something I would recommend except under very controlled conditions in very shallow water, it is something that should be experienced. It can be accurately simulated safely above water by simply breathing a tank down until you can't get any more out of it. The only difference is if you are down 15-20 ft (5-7M) you will get another couple of breaths as you accend but otherwise the feel is exactly the same.