running out of air

[spectrum]

What are indications that a tank is getting low, other than the gauge, when you are underwater or do you take that last breath and that's it?

!

As mentioned in most cases you will have very little if any warning in terms of work of breathing.

However there should be a big safety margin between common sense and OOA. Even without "gas planning" for the dive you know that the SPG will show a steady pressure reduction. If that's not happening the light bulb should go on. Similarly it does not take too many dives at all before new divers know that they are good for :30, :40 or whatever for a given depth profile. Assuming you have at least a time piece and all things being reasonably equal you should know when to surface because there is no air fairy.

When in doubt, get out.

Pete

 

[Frosty]

In an extremely controlled situation I have deliberately run myself OOA on two occasions.
-Please note I did say extremely controlled situation. I can say that running a tank OOA and shutting the tank off feels different.
The last few breaths feel progressively harder to take until the last suck of air. There is a definite feeling that something isn't right but you only have four breaths to work that out..

 

[jonhall]

I'm surprised, and doubly surprised that no one else brought this up (unless I missed it): didn't you experience this in your OW training?

Since this would probably be directed to me, the OP, my PADI training in 1998 did not include this in the training. In the event that I just don't remember that far back, and they turned my tank off, it surely wouldn't have made or didn't make an impression on me, being only a few feet down in a swimming pool!

Not sure I was even thinking at that time what potential emergencies (other than DCS) there could be in scuba, let alone what to do if I ran out of air, which, btw, was not the question/concern in this thread.

Thanks all for some interesting comments.

Having made a statement above about not thinking of potential dangers and running out of air, buddy breathing was practiced on several occasions and once in check out dives.

 

[tursiops]

Since this would probably be directed to me, the OP, my PADI training in 1998 did not include this in the training. In the event that I just don't remember that far back, and they turned my tank off, it surely wouldn't have made or didn't make an impression on me, being only a few feet down in a swimming pool!

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?

 

[phoenix31tt]

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

 

[lowviz]

I would suggest that you try it with a clipped-on 40 cuft or so. It will only cost you a VIP for a worthwhile experience. The cylinder is supposed to quit supplying at the IP setting of your reg, I beg to differ.

Just don't descend after you breathe the cylinder down, you risk water entering as the pressure difference would then be backwards.

Keep the secondary reg in your mouth. With your main gas supply at the ready, ascend with the depleted cylinder and note that you will get an additional breath or two. Wait for it.

OK, flame on...

 

[boulderjohn]

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 just looked at a PADI log book from that era, which lists the skills required for each confined water dive for the OW course. Air depletion is not listed, which is frankly a surprise for me.

Even if it were listed, that does not mean it was part of the course as it was actually taken. I was certified in a resort area in Mexico, and my confined water training took about two hours in a pool that had a maximum depth of maybe 5 feet. We skipped many skills. They are all signed off in my log book, though, something I never noticed until many years later when I took the DM course and had to demonstrate skills I had never learned in my OW class.

 

[tursiops]

I just looked at a PADI log book from that era, which lists the skills required for each confined water dive for the OW course. Air depletion is not listed, which is frankly a surprise for me.

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.

 

[boulderjohn]

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.

I always assumed that the air depletion exercise was in the program from the start, and that is why I was surprised it was not in the log book I have from that era.

I always believed it was an obsolete skill going back to an era of inferior regulators. When I became an instructor, I was told to tell the students that the purpose of the exercise was to allow them to feel what it is like as their air become more difficult to breathe so that they can recognize it and respond quickly and appropriately. That baffled me from the start, because with modern equipment, there is no such experience, and that has been true for a very long time. I have never felt any transition between getting air to not getting air while in the pool.

 

[lowviz]

...//... with modern equipment, there is no such experience, and that has been true for a very long time. I have never felt any transition between getting air to not getting air while in the pool.

Leave your reg set disconnected from a cylinder for this test. If you put your modern secondary reg into your mouth and try for that last desperate breath you won't get anything? Right?

BTW, Wet your thumb and cover the primary reg's inlet. Now try try the same thing. Great way to tell if some rental shop is renting you a wet breather.

---------- Post added October 14th, 2015 at 02:34 PM ----------

Re-reading this thread, I just noticed that I had overlooked post #6. The experience, as reported, is quite believable.