I've had three that I can recall. One was accidental, the other two
intentional.

The accidental one's been posted before. I was 128 feet deep, at cork rock
in Blue Springs, by myself, when I ran out of gas. Three of us started down.
One diver had ear problems and the second one escorted him to the surface.
This was in the mid 60's, when I was much more bullet proof than I am these
days. At any rate, I had everything needed for cave exploration, a
galvanized 72 cubic foot tank, an unbalanced single hose regulator, light,
newly purchased depth gauge and a dive watch. I did not have a BCD, octopus,
SPG or any kind of redundant gas supply, including a buddy. Except for the
buddy, I was better equipped than most divers of that time.  At the bottom,
where the current flow is so strong that you can't penetrate further, I
pushed a rock into the flow. Instead of going down, it went up, then down,
then up . . .  I was fascinated. After a few minutes, I noticed it was
getting harder to breathe.  Back then, that's how we knew it was time to
surface.  Apparently, I missed the first clue, because about a breath and a
half later, my tank was as empty as I could get it.

Curtis can probably give a more accurate description, but my recollection is
that I was about 45 feet back from the entrance which was about 45 feet
below the surface. It's safe to say that I broke all rules, and perhaps a
few records, on my way out and up. I deserved to be bent like a pretzel.
Only the gods of diving know why I wasn't. I sure could have used a pony on
that dive.

The second and third times I ran out of gas, both while spearfishing in the
Dry Tortugas, were intentional. The second time, I had surfaced and, at some
time since surfacing, dropped my favorite lobster snare. I dropped to about
40 feet, to where I could see the bottom, and swam against the current,
looking for my snare. I knew I was low on gas, but it was my favorite snare.
Just as I spotted it, it got hard to breathe.  This time, I had a balanced
first stage.  Hard to breathe meant I was very low on air.  I considered
descending to get my snare, and then thought about it some more.  I watched
the snare disappear in the distance as I headed up.

The third time, I shot a prize winning Black Grouper early in the dive.  He
managed to wedge himself, and my spear, under a rock. I spent the rest of
the dive trying to get him out. Again, I knew I was running low on gas, but
by that time, my buddy had arrived.  I confirmed that he had enough for both
of us and made the conscious decision to run out rather than abandon the
fish.  I hate to kill fish I can't recover, particularly when they're likely
to win me money.  I did not get that fish, or my spear.  When I ran out, I
gave my buddy the OOA signal, expecting him to hand me a regulator.  You can
imagine my surprise when he continued to work on getting the fish out from
under the rock. I took his alternate, proving that you can, in fact, breathe
off someone's combination inflator/alternate, until he realized what was
going on and trade me his primary. He had misread the signal, thinking I was
low on gas rather than out.  I suppose he was mislead by the fact that,
until then, I'd always surfaced with more gas than he had, but we still did
a review of critical signals when we returned to the boat.  He's a PADI
Instructor, by the way. Sorry, but just had to include a cheap shot at PADI.

I rarely carry a pony, or a stage bottle.  I don't dive in caves any more,
but still do some relatively deep, modest decompression, and solo dives. I'm
much more likely to carry a pony and/or deco gas on those dives.

Lee

Never one.

No reason for it to ever happen if you pre-flight and follow the very simple
rules.

Closest I have come is a guy I love dearly took all his gear off and tossed
it to the bottom during a drift dive off Ft. Lauderdale, and another guy I
love dearly handed him the long hose while I went and got his gear off the
bottom.

Sure you can. Gas transfer takes place as long as the partial pressure in
the tissues is greater than the partial pressure in the blood stream and as
long as the partial pressure in the blood stream is greater than the partial
pressure of the gas in the lungs.  It will eventually reach equilibrium, but
you may not be around by the time it does.

Lee

No I didn't and remember Boyles law

Drop the "also" and you have it right.

Bingo.

I took an AL80 down and opened the valve; it takes about 4 to 5 minutes
(someone will quote the original post right away to make me out a liar) to
empty. And is *really* loud. I have toyed with the idea of making a simple
block that I can connect to a bottle to see how long it takes a burst disk
failure to vent at depth. Had several go off in the shop, always when
fighting to stay awake; the AL40 was the fun one, it spun like a top and
knocked all kinds of stuff over.

Even IP decreases with ascent, allowing a breath or two, there is gas in
your BC....

What kills most divers is ego and panic. Half are dead before they get in
the water.

In tests at Eagle's Nest in 2006 by Curt Bowen, it took 22 minutes to
empty an aluminum 80 with a failed HP hose, regardless of depth.

It looked spectacular and worried my Instructor at the time

I have to agree now after reading other peoples posts on the matter, however
if I remember the hose stopped flapping around and bubbling before we did a
SS and we certainly treated it as an out of air and shared air ro the
surface