Interesting I get to be the first to respond to this one.  Here's some
suggestions, from a semi technical perspective.

Regarding who grabs what, it's a common belief that an OOA diver will almost
always grab your primary regulator.  I don't believe in common beliefs, so I
try to ensure things can happen only one way.  With my kit, you would find
it very difficult to grab anything other than my primary.  It's in my mouth,
held loosely enough that neither it, nor I, get hurt if you grab it
unexpectedly.  My alternate is on a shorter hose, smaller, black, and on a
necklace just below my chin.  You literally have to reach past my primary to
get to my alternate.  Obviously, I plan on using the alternate.  As an
aside, my alternate, like my primary , is a high performance, high quality
regulator.  The last thing I want to do is get cheap on the regulator I'll
be using in an emergency.

The issue of gas management is also kind of important.  For anything but the
most recreational of dives, meaning no, or very little decompression, the
norm is for each diver in a buddy team to carry sufficient gas to get
himself and his buddy to the surface safely and at least a little more.  The
rule of thirds handles that for my pretty well.  I use one third for the
dive, one third to get myself out of the dive, and one third for whatever
emergency comes up, including an OOA buddy.  That applies to travel gas, if
any, bottom gas and deco gas.

Alert divers don't often have to share air.  I've done it a few times, but
each time, I saw the situation developing and made the offer.  Nobody has
ever taken my regulator.  I've always given it to them.  I give my primary.
Once, a buddy had a regulator failure.  The first stage stopped working.  I
saw the buddy coming and headed for him, breathing my alternate, with my
primary in hand.  Once my wife/buddy had stayed a bit shallower than I did,
but thanks to some excitement during the dive, had used a bit more gas than
I did.  I needed to do a deco stop, she didn't.  I had plenty of gas, she
didn't.  Rather than separate, I handed her my primary and I used my
alternate.  We both did my deco stop and ascended together.  The third
incident was during a deco stop.  My buddy was using mix, I was using
nitrox.  He had only mix, I had a 40 cf sling tank full of 50%.  Once I was
sure that I had met all my deco obligations, I passed off the deco mix
alternator so he could us my helium free mix to ensure he was not only
nitrogen safe, but helium safe.  It probably wasn't necessary, but we had
the gas, and it's better to be safe than sorry.

The only time I've been involved in a situation where someone took the other
diver's regulator without it being offered, I was the OOA diver.  Last year,
on a spearfishing trip, a grouper I had shot managed to get under a rock,
taking my spear with him.  I didn't want to lose the fish or the spear, so I
spent most of the dive trying to get both back out.  I did not succeed.  In
the process, I used my gas at a faster than normal rate.  I checked to
ensure my buddy had plenty of gas for the two of us, and deliberately used
mine to try to get the fish and spear.  When I ran out, I signaled I was out
and, much to my surprise, he turned away and continued to try to get the
fish.  I later learned he had mistaken my signal for low on air.  He was
head down by the rock when I took what was available, his combination
inflator/alternate.  It surprised him a bit, but not for long.  We traded
and headed for the surface.  It was a shame about the fish and spear, but
you have to have your priorities.  Note that I did not accidentally run out
of gas, or deliberately do so without knowing my buddy was right there and
had enough for both of us.

At any rate, the only time anyone grabbed a regulator unexpectedly, I
grabbed what was available.  I did not do it in a panic, I did it
deliberately and, had the primary been available, I would have taken that
instead since that's the right one to have when using a combination
inflator/alternate.  Take this for what it's worth.  I've been diving for 45
years and may not be representative of what a less experienced diver would
do.

Lee

the difference here is that he grabbed it as opposed to you handing it
to him.  Handing him you primary makes sense as it is (slightly) more
easily accessible and the OOA diver may be panicking.

In your case, he grabbed the secondary, so all was well.

Only had one serious out of air from a guy in a group I was leading at 25m.

O.K. at max depth of 30m, 60% of a tank left at the turn as we headed back
to the surface. Supposedly trained to Advanced Standard in PADI but narced,
hyperventilated his tank away in no time and panicked. Left his buddy and
finned towards me for all he was worth with his pressure gauge held out
straight for me to see. He had 10 bar left at 25m and all the out of air
signals from his training went completely out of the window.

I gave him my primary just before he grabbed it and then held him firmly by
the BCD, looking him straight in the eyes, as I reassured him and calmed him
down before he breathed my air away in a similarly quick time. Quickly
checked his buddy was paired off with someone else, that all others were
O.K. and then brought us all back to the surface.

Important lessons and success factors for me were :
- Calming him down as quickly as possible
- Expecting the unexpected and allowing 33% of my air for the unexpected in
the plan
- Debrief session afterwards with all the others
- Debrief with the OOA guy (one to one) praising him for the stuff he did
right as his self confidence was completely shot at that stage
- I knew the guy quite well but he did not respond as he or I would have
expected

Bottom line .... my humble advice is expect the unexpected and always build
contingency into your plan

Well done for handling the situation calmly

Martin

I recently was involved in a OOA situation - my buddy's reg free-flowed as
we were coming up from 30m off the UK south coast, and lost him his air
double-quick. We handled the whole thing fairly well - he went for my
octopus and up we went, slowly and calmly but owing to prior delays (and
this is the bit that makes me plan to be more conservative in the future)
now without air for proper stops. We were fine, but it's made me wonder
about the difference between how things are supposed to go and real-world
situations. A tech-diver mate says they're taught to expect the OOA diver to
grab their primary reg (they can see it, and see that it's working), and
that's the idea behind inflator-octopuses (octopi??) as well - they take
your primary, you use the inflator reg.

So - what really happened when you or someone you know lost their air?

Bernard

I've never been in an OOA situation (1400+ dives).

But I keep my octo partly hidden and my primary in plain sight - I
expect anyone who needs one of my regs to take the one in my mouth.

If I were asked to give a reg, I'd give the reg in my mouth: the donee
may need it more than I, and I can always find my secondary and clear it.

With the increasing number of inflator/secondary regs, it should become
a rule that the reg in yer mouth is donated.

Even when yer secondary is on a long hose, I believe the primary should
be donated immediately, and when the excitement has calmed down the regs
can be swapped for ease of ascent.

esg

I lost my air, free flow at 30m. I switched to my pony. We were within
no-deco limits. My buddy and I made a normal-ish ascent. We came up rather
faster than we might have to 15m (but still not so fast as to make our
Vypers alarm) and came up at the normal rate from there, inc the usual 3min
@ 5m stop. On the surface my pony had 70 bar in it (200 at start of dive)

It was my FIRST dive with my pony, which I reckoned more than paid for
itself there and then!

Ken

I've been in 3 OOA situation - 2 where my reg free-flowed (cold water
freezeup), and one where a buddies reg free flowed (sand in reg).  The
first time (my 1st free-flow)it was a complete f*ckup - I panicked a
little, ignored my buddy (who was trying to pass me his reg), and I
ended up doing an emergency accent from ~25m.  Luckily I remembered to
"scream" on my way up.

After that incident the guys I dive with spent a few dives practicing
for these emergencies.  The next time it happened (sand incident) we had
a bit of warning (reg preformed poorly before free flow).  My buddy
signaled that he was having a breathing problem, so we started
surfacing.  He free-flowed at ~10m; I passed him my secondary, we
continued our ascent, did a safety stop, and surfaced without incident.

The last time my reg free-flowed without warning - one minute I was
breathing fine, the next I was surrounded by bubbles.  I "sipped" from
my reg and got my buddies attention.  He had his secondary in my hand
within seconds, and we surfaced normally.  I don't even remember being
particularly stressed that time.

Lesson learned - practice makes perfect, and can make it so that the
proper response is instinct.  Makes responding to such a situation real
quick & easy - almost mindless.  Other lesson learned - stop using
rental gear.

Bryan

I had my primary reg yanked from behind me with no warning on a wreck at
about 120'. I was using a traditional BC and hose setup. I was breathing
the short hose, and my 39" secondary was routed under my right arm and
the mouthpiece was stuffed through a loop of surgical tubing that was
zip tied to my BC. The OOA guy was slap out of gas, and wanted immediate
upness, so I had to fight with him while I got my secondary into my
mouth. By the time I was breathing again, my buddy had jumped in to help
keep the guy from dragging me to the surface. It's a good thing he
didn't have any gas to inflate his BC. We got the guy slowed down and
got him to calm down, and I showed him that I had 2000 psi left in my
single 108 ( which had a Y valve and 2 first stages) and 2000 psi of O2
in a 30 cu ft tank. The three of us made a proper ascent and stop. It
turns out that the OOA guy was a vacationing walk-on who had zero
experience in those conditions and that depth. The divemaster had put
him as a third in a buddy team, and the other 2 thought he had aborted
during the descent.

In another incident, I was doing a 200 ft wreck with my regular buddy
and someone I had just met but who had been diving to that depth several
times with my buddy. When we were going over the plan, I didn't think
the guy had enough gas for what we were planning, so I offered to
shorten the bottom time, but he insisted that it was no problem, so we
went. We did our planned bottom time, and left the wreck in a ripping
current. My buddy one bag as we left the wreck, as agreed with the boat
captain. The plan called for the other guy and me to shoot our bags from
80 ft. Our deco stops started at 150', and when we got to 110 the guy
signalled to me that he was out of gas. He was very calm, and I gave him
the long hose I was breathing from and went to my necklaced secondary. I
thought the guy was too calm, and when we got to 80' he didn't shoot his
bag or respond to my signals that he should do it, so I took his bag and
shot it so the captain wouldn't be looking all over for him. I was right
in his face and his eyes were focused and following me, so I figured it
was just his way of dealing with screwing up. I gave him the reel with
the bag I shot for him and he handled it ok. When we got to 70' he did
his gas switch ok, and the rest of the deco was uneventful.

There was another incident where the diver was not out of gas, he had
dumped all of his gear, and still calmly signalled for my long hose.
That story has been posted here several times ;-)

I don't like the octo/inflator. Most of them are hard to work on, and
unless you practice with it, controlling your buoyancy while attached to
another diver who may be doing something stupid may be difficult. I
prefer the necklaced secondary, which for most people costs just a piece
of bungie and a new hose.

My primary second stage failed on descent while diving off Cozumel.
Some shop monkey had installed the diapraghm incorrectly and it pulled
away from the housing.  I switched to my octo and continued the dive (I
also had a pony bottle) and stashed the primary so it couldn't be
mistaken for an air source. I sorted out the problem when we got back to
the boat and dove without incident for the rest of the trip.

I have had once incident where my buddy and I were crossing through
the surf zone and he had bit through his mouthpiece, lost his 2nd
stage, and had paniced... This was back in the days when we didn't
have SPGs nor octos... We were within a couple of feet of the surface,
but he was attempting to strip the reg out of my mouth... I grabbed
his tank from the rear and shoved him up to the surface... I held him
that way for long enough for him to calm down and then we swam back to
shore... I don't think that I ever dove with him again...

OK, I admit it, I ran out of air, ONCE.  I had just got the bottle back from
"VIP" and the shop idiot didn't tighten the valve.  the lower the pressure,
the faster the leak. Was at the bottom of Blue Springs in Orange City FL.  I
looked at my gauge before we entered, was 2800, by the time we hit the
bottom (110') it was 300.  I was trailing so no one saw it.  I grabbed my
wifes fin and asked for the secondary, and when she saw the bubbles coming
from my tank, she gave it to me without pausing.  I didn't panic, for one
reason, training. I knew I could go back up without a problem, so I decided
to just get my wifes secondary, call the dive, and go back up at a
reasonable rate. It really helps to have a dive partner who you have
practiced with, and can rely on.

gary Owens

If a shop monkey do something to screw up your regulator on the
suuposed mandatory yearly maintenance. Then I go to another shop and
the tech knew what happened and fix it.

How long can I co before I get it to service...I don;t want the shop
monkey to screw it up again.

It would be interesting/usefull to have the previuos posters add the
following detail to their posts:

How many dives they have ever done/ dives per year.
How often they have their kit serviced.

as it seems to be that nearly all incidents were down to poor kit
maintenance rather than luck/training.

I am part of a dive operation that insists on regulator service (for
staff and students) every 100 dives/ 12 months and

given

I do 250 (cold water) dives per year, plus 100+ pool sessions, have 6
colleagues and countless students passing thru -
in the four years I have been diving we have NEVER seen a free flow
incident or real reg failure (ie not counting where a student spits a
reg out and holds it up the wrong way until we sort it).

Is this luck or just the atitude to kit?