running out of air

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Training Bulletin, 2Q1994, p5, says:
"Q. Are there any additional skills that must be taught when accepting referrals from other training organizations?
A. Yes. The student must also demonstrate mastery of the following skills in confined water: the Underwater Swim Without a Mask and the Air Depletion Exercise from the PADI Open Water Diver course. By conducting these skills the instructor ensures that the non-PADI student has mastered them. In addition, because these two skills are not required in the PADI Scuba Review Program, we have added them to the Skill Evaluation slate for your convenience."
This says to me that Air Depletion was in fact part of the 1998 course, since it was required in 1994 and is still required.
I only have TBs back to 1994, so cannot find out if it existed before that.

Pulled out my old books: PADI OW Manual published 1990, 1994. Module 3 covers out of air and alternate air sources. Explains using alternate air sources.

Diver's Logbook published 1991. For module 3 skills, alternate air sources is listed, but nothing about out of air or air depletion.

Seems like for what the course cost, I should have received newer books!

It is very likely - almost certain - it was included in your training in 1998. I do believe you don't remember it, but I have to wonder why. Did you think you didn't need to breathe only a few feet underwater?

I guess I wouldn't remember it, for sure, if it didn't happen! But do remember alternate air sources and buddy breathing. Love breathing a few feet underwater...it's my first choice whatever depth I'm at!
 
It's good to know that breathing a tank down doesn't feel the same as breathing off a closed valve (which is almost instant)... from what i'm reading from the guys that actually breathed tanks down you actually feel a difference before you run out, my reg supposed to be a high performing reg so maybe i would have less breathes (don't hope to find out), but basically you have some level of warning. Even if it's two breaths... that's alot of time to find your buddy (assuming semi-correct buddy practices)...

good information to know regardless

This seems to be the general consensus from the thread responders that even with modern regs, balanced or unbalanced, YOU WILL get some kind of warning in the form of change in regulator performance and difficulty in drawing air.

If this is the case, why are we still teaching Air Depletion by shutting of the valve. Shouldn't we be teaching students to immediately abort the dive at the first sign of Reg performance change and/or difficulty in drawing air as these are the impending signs of OOG?
 
I would HOPE that the modern courses teach that : "when it gets hard to breath, come up"...:shakehead::rofl3:

Also, if instructors REALLY wanted to teach this stuff, they would take a set of doubles in the pool. One tank is empty, other full... squirt a 100 psi across the isolator, shut it and give each student a chance to actually feel what a tank draining is like. It is probably too much bother and expense for most instructors, but it could be done... the student would not even have to wear the doubles, just lay the tanks down on the bottom next to them and have them keep their primary reg in their hand, and their normal (functioning) gear on.
 
It seems to me we are training around the issue nowadays.-So basicly get down to 1/4 of your 200/3000 level and you should be on the boat or at the very least on the line.
The red "line of death" should never be crossed etc etc seems to be being well drilled into students.
 
I would HOPE that the modern courses teach that : "when it gets hard to breath, come up"...:shakehead::rofl3:

Also, if instructors REALLY wanted to teach this stuff, they would take a set of doubles in the pool. One tank is empty, other full... squirt a 100 psi across the isolator, shut it and give each student a chance to actually feel what a tank draining is like. It is probably too much bother and expense for most instructors, but it could be done... the student would not even have to wear the doubles, just lay the tanks down on the bottom next to them and have them keep their primary reg in their hand, and their normal (functioning) gear on.

No they don't. They teach Air Depletion exercise where the tank valve is closed down. As mentioned by others, doing so simply cuts air immediately. But it appears that that's not reality in a OOG situation. Rather, the air drawn gets harder and harder. Based on accounts in some posts above, you'll have a few breaths before vacuum. The "warning" signs are not taught across any agency standards afaik.
 
No they don't. They teach Air Depletion exercise where the tank valve is closed down. As mentioned by others, doing so simply cuts air immediately. But it appears that that's not reality in a OOG situation. Rather, the air drawn gets harder and harder. Based on accounts in some posts above, you'll have a few breaths before vacuum. The "warning" signs are not taught across any agency standards afaik.

This is correct. Breathing gets progressively and rapidly more difficult. Ascending give a breath or two more.
During a pool session of our OW, we had the opportunity to breathe down a tank and see what it feels like.
I've done the same thing in OW: I had a 40cf deco bottle full of EAN50. I used about half during deco on our first dive. On our 2nd (non-deco) dive, I switched to it puttered around at 40' or so, and headed up. It started getting hard to breath off during the safety stop, so I switched to my back gas to get back on the boat. That deco reg had one of the little button gauges on it. Blech. No more of those...


Sent from an old fashioned 300 baud acoustic modem by whistling into the handset. Not TapaTalk. Really.
 
I have purposely run OOA just to see what it's like. The deepest I've done this test was in 30 feet, but most of the time I'm right at the exit in about 10 feet.
On an unbalanced MK2/R190 (both unbalanced) the draw down is very gradual. I would say I had at least 20 or more breaths from the time I noticed difficulty to where I was sucking hard enough to call it completely drained.
With a balanced setup like my MK20/G200B, from the time the draw down starts within 5 good breaths it's pretty much down to pulling hard.
I did a comparison once in about 10 feet of water to see what the difference was between a balanced reg and unbalanced reg when they start to breathe hard. For this test I was using a balanced piston first stage. I switched to my unbalanced octo when the gauge read about 200 psi.
It wasn't really noticeable in shallow water but when the tank got down below 130 psi it did start breathing hard. By the time I could barely get any air out of the unbalanced second I switched to my balanced primary and I could get full breaths of air. I started to breathe that down to where it pulled hard, then just to see the difference I switched back to my unbalanced reg and had zero. So I switched back to the balanced and amazingly it still was delivering some air, but then after about two or three more draws it was pretty much gone.
So using a balanced second in my test really made a difference. They are air assisted in opening the poppet, so even with ridiculously low tank pressure they will deliver air down to the last drop.

I have never done this test in deep water. I will never do the test in deep water unless it's intentional and I'm set up for it.
I have never run OOA unintentionally because I had it hammered into my brain that there is simply no excuse for divers to run OOA.
I was told that if a diver is irresponsible enough to not pay attention and manage air supply then they have no business diving, period.
 
I have purposely run OOA just to see what it's like.
So have I, on purpose also. I solo dive more often than not. My gas supply is the only thing that I can count on.
I did a comparison once in about 10 feet of water to see what the difference was between a balanced reg and unbalanced reg when they start to breathe hard. …//… By the time I could barely get any air out of the unbalanced second I switched to my balanced primary and I could get full breaths of air. …//… So using a balanced second in my test really made a difference. They are air assisted in opening the poppet, so even with ridiculously low tank pressure they will deliver air down to the last drop.
Thank you for that observation, it is most interesting. It also agrees with my past experiences. Fine points like this aren’t commonly reported because doing anything below 500 psi is agency taboo.

I used to have a fairly diverse collection of primary and secondary regs. I’ve since found one combination that I love and stick to it, sold or donated everything else. Now, everything “feels” the same.

Yes, there is a draw down period that had better send chills along your spine at its first awareness. However, one can’t be aware of the subtle warning if one doesn’t practice IRL. Which reminds me, I haven’t practiced that skill since standardizing on my reg combo…
That first “odd” breath is where one should start thinking about weights and orally inflate at the surface while initiating an immediate exit.

Turning off a valve leaves you with the reserve in your hoses (nothing), sucking down a pony gives you a bit more, a single gives a reasonable warning, doubles give even more. All this is contingent on being able to instantly realize that something is wrong with your air supply when something does go wrong with your air supply.
I have never run OOA unintentionally because I had it hammered into my brain that there is simply no excuse for divers to run OOA.
I was told that if a diver is irresponsible enough to not pay attention and manage air supply then they have no business diving, period.
We have all had the NDL and reserve gas mantra drilled into us, but things in real life don’t always go as planned.

The mantra protects instructors from lawyers, but does little other than adding fear to the already stressed diver if the diver discovers, a bit late, that line has been accidentally crossed.

If something can happen, sooner or later it will. I choose to continue to practice dealing firsthand with the exceptions rather than harping on a denial of their existence based on superior instruction.
 
The closest similar feeling to a low on air tank that I can think of is when the valve is on just enough to allow some small amount of air to pass. Still not quite the same and not progressive but more similar then a completely closed valve.
 
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The closest similar feeling to a low on air tank that I can think of is when the valve is on just enough to allow some small amount of air to pass. Still not quite the same and not progressive but more similar then a completely closed valve.
Or when some dips### hydros an ally tank and doesn't clean/dry it properly. Then the feeling as the filter progressively clogs with Ally dust is similar.
 
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