What is the deepest you can do an OOA?

[nereas]

The deepest I have done one from (my tank valve clogged and I hadn't strapped my pony on for that dive) began at about 75 ft. I had just exhaled when I tried to take another breath and thee was nothing so my lungs were largely evacuated. It happened about 5-6 years ago, and it was very difficult to make the ascent as there wasn't a lot of air in my lungs to expand as I ascended. ...

I completely agree.

Upon finding out that someone has run OOA, they won't have a deep breath of air in their lungs like a freediver would.

Thus the ascent is going to be quite quick.

And therefore the risk of DCS would be quite significant, from any depth deeper than 33 fsw, at least according to Haldane. It depends on how long someone had been down.

 

[Puffer Fish]

Breathing from an ABLJ used to be taught and was a normal skill at the advanced level (at least withing BSAC and CMAS. For some time the FENZY even came equipped with a one-way breathing valve to make this easier. It was abandon due to fear of lung infections.

You sometimes amaze me... I used a FENZY for more than 10 years ... and yes, you could breath off of one...which is about as easy as breathing off a tank without a reg on it.

On how deep... you may remember the Navy training center tank in San Diego... I've seen someone do a free accent from the bottom of that tank..which is a lot deeper than 120..

We used to actually do a 90 ft one... which was not that hard...stupid, perhaps, but not that hard.

 

[Web Monkey]

Well if it can be done, I'd take the lung infection over suffocation. Can you pull a breath off today's BC (standard power inflater/deflater) or is their a pressure issue? I'd assume since you can vent the gas off, you should be able to inhale it... does it get more difficult with added depth ?

If you're properly weighted, it's not especially productive to breathe off a BC, since you'll be venting it to compensate for the gas you've used from your tank during the dive, so by the time your tank is empty, your BC will be empty also.

Terry

 

[Tigerman]

If you're properly weighted, it's not especially productive to breathe off a BC, since you'll be venting it to compensate for the gas you've used from your tank during the dive, so by the time your tank is empty, your BC will be empty also.

Terry

Well, if there IS some gas in it that expands as youre bolting for the surface, it should be possible to suck it in just to get that extra 2 meters before you pass out I guess?

 

[drbill]

Please refer to the PADI open water book, in there you will find the following statement or something similar to it. Diving within recreational depths and within NDL you can always complete and Emergency Free Swimming Ascent.

Well and "good" in theory... however, in actual practice I would beg to differ. It depends on several parameters that may not have been considered.

When I made my emergency ascent, I kept my weights on to ensure I ascended at the safest possible rate given my breath-holding ability. My planned ascent rate was 1 ft per sec, and my ascent time was 70 sec from that depth. I figured if I absolutely had to, I could drop my weights to ascend more quickly if I felt I was going to black out.

Again, younger divers in good shape may have no problem doing an ascent from 100+ feet. Back in the days when I was a record-setting competitive swimmer, I doubt I would have had a problem. However, many of today's divers (like the population in general) are not in that kind of shape... including me!

 

[Thalassamania]

You sometimes amaze me... I used a FENZY for more than 10 years ... and yes, you could breath off of one...which is about as easy as breathing off a tank without a reg on it.

On how deep... you may remember the Navy training center tank in San Diego... I've seen someone do a free accent from the bottom of that tank..which is a lot deeper than 120..

We used to actually do a 90 ft one... which was not that hard...stupid, perhaps, but not that hard.

With a dry suit (or very little neoprene) and a single I still use a FENZY.

 

[miketsp]

Do you remember what Haldane got in his goat experiments?

2 ATAs n'est pas?

So that would give you 33 fsw, technically speaking.

The 2:1 ratio from the Haldane experiments would only give you a 33fsw limit if the tissues were saturated at the start of the CESA.
On my Suunto Dive Manager SW log I can look at compartment loadings at any point in the dive and on the majority of my dives for a good part of the time the 2:1 ratio would not be a limit even at depths much deeper than 33fsw.

Of course nowadays the 2:1 limit would not be considered either safe or rigid.

 

[beester]

In my agency until a few years ago it was a mandatory test for certification on level rescue or divemaster. (equivalent).

Rescues had to do a fully equipped free ascent (regulator out of mouth in hand)from 100 feet till 30 feet.
Divemasters had to do a fully equipped free ascend from 140 till 40 feet.

Not until surface to prove you were in control of your buyancy during the whole test and also obviously because of the last 30 feet compounding to the biggest pressure change and percieved as most dangerous.

Anyway lots and lots of people did it... and always told that it was easier than they thought it would be. Also people stated that it improved their awareness about what is possible. So these are no sub-escape exercises by navy men but normal divers in all walks of life who had to perform this in local circumstances (so not in a pool but in quaries, sea, whatever).