Anybody done an Emergency Ascent?

[O2BBubbleFree]

HI all,

When I was in my OW class back in '94 the course director was an old Navy diver w/ about a million dives. He told me that he knew an individual that had done an emergency ascent (swimming to the surface at safe rate, exhaling all the way) from MORE THAN 90'. He seemed like a good guy, but this is a second-hand story from someone I don't really know.

On this board I've read that it's not practical to expect to be able to do an emergency ascent from more than 40', and 90' seems like an awfully long way.

I've only tried it from 15', for training, and never had to rely on this method, praise God. What's the deepest that anyone has actually done an emergency ascent from (sucessfully)?

Yes I know about buddy system, back-up regulators, etc, etc, so let's not re-hash all that, 'kay?

 

[glbirch]

I don't see this as unbelievable. I've done 25' in training but never a real one (knock on wood.) 90' would only have been a minute and a half or so, which a fit person should be able to hold their breath for. (Exhaling gently all the way of course.) Not everyone could do it, but the unsuccessful ones wouldn't be telling stories about how they didn't make it...

Don't some navies train their people for emergency ascents from submarines at those depths?

 

[Gary D.]

We trained to do them in the Submarine Escape Training Tank.
It had several locks along it's sides down to 100' with a tank depth of 119'. We did a lot of Free and Buoyant assents in training and some for real.

It's a weird feeling to exhale for almost 2 minutes. On Free assents your blowing fairly strong. On Buoyant assents you are actually yelling in the hoods mouthpiece.

They said in theory it could be done from 600’ but I would not like to be the one to try it even though it worked on paper.

"DO NOT TRY THIS WITHOUT THE PROPER TRAINING"

Gary D.

 

[Gary D.]

I don't see this as unbelievable. I've done 25' in training but never a real one (knock on wood.) 90' would only have been a minute and a half or so, which a fit person should be able to hold their breath for. (Exhaling gently all the way of course.) Not everyone could do it, but the unsuccessful ones wouldn't be telling stories about how they didn't make it...

Don't some navies train their people for emergency ascents from submarines at those depths?

You don't have to be in good shape. Your lungs are going to expand at the same rate nomatter who you are. It is surprising at how hard you exhale to do this safely. SO DON"T TRY IT.

All the submarine Navies train for escape with both free and buoyant assents from various depths.

Gary D.

 

[Charlie99]

I did a practice ESA from 88'. 2 min 20 sec ascent time. Never felt out of breath and arrived at the surface quite comfortable. I had close to zero excess N2 load since I did it at the beginning of the first dive of day. Quick descent, immediate ESA. Self check on surface, then immediate redescent for a dive with normal ascent and stops 50 minutes later.

The trick is to merely leave the airway OPEN, rather than contracting the chest or diaphram to actively blow out air. In other words, leave your lung volume constant and let the excess air bubble out. Don't try this unless you have complete voluntary control of your epiglottis.

 

[Charlie99]

Your lungs are going to expand at the same rate nomatter who you are. It is surprising at how hard you exhale to do this safely..

My experience was quite different. At the reasonable emergency rate of 60fpm you will have 30 seconds or so to dump the lungful of air that appears as you go from 33' to the surface. In the deeper zone, the rate you generate excess air is even slower.

A person that has difficulty doing a full lung exhale in 30 seconds (or even 10 seconds!) probably shouldn't be in the water at all.

 

[Gary D.]

My experience was quite different. At the reasonable emergency rate of 60fpm you will have 30 seconds or so to dump the lungful of air that appears as you go from 33' to the surface. In the deeper zone, the rate you generate excess air is even slower.

A person that has difficulty doing a full lung exhale in 30 seconds (or even 10 seconds!) probably shouldn't be in the water at all.

I wasn't talking about the same rate at depth. I was refering to the human body. A bubble is a bubble nomatter who's body it is in. Physics is not going to change from one body to another.

As you get shallower the bubble will expand faster than at depth. One could, in theory, hold their breath from 600' to 500' without expansion problems. But from 10' to 0' could be fatal.

Gary D.

 

[Rick Inman]

DON'T DO THIS

There is a place I dive where at the beginning of the dive I like to start out by dropping down to 30 feet and doing a free accent. Good practice, I figure. If I ever really need to do one, it would be nice not to have it be the first try.
I've found that if I blow too fast, I do run out too soon. After I did about four of them, I found just the right flow so that it's comfortable. But remember, DON'T DO THIS OR YOU'LL DIE
Here is DrBill's post on his 70' OOA, solo accent. If you haven't read this, you'll enjoy it!
http://www.scubaboard.com/t37780.html

 

[H2Andy]

my Rescue instructor did an emergency ascent, for real, from just over 80 feet.
he was fine.

i also spoke with a diver in Bonaire who did an emergency ascent from 70 feet
and got type II DCS and had to ride the chamber.

obvioudly, neither person held their breath.

 

[DORSETBOY]

Almost! did my rebreather training on the 'dolphin', the damn thing had a leak at 18m, flooded the breathing loop and gave me a mouthful of acidic tasting water when I tried to breathe.. being..

a). stupid.
b). unattentive.
c). distracted by the world's most friendly wrass!!!!

... I'd managed to let my alternate slip from its usual position and it was now trailing out of arms reach behind me. My instructor meanwhile had swam off 10 m ahead and going fast. I cr*pped myself, looked up, thought mmm tempting and then thought it would look a bit cr*p if I did a CESA as it was a week after my IDC! Ended up swimming like mad after my instructor and grabbing his alternate, my eyes were like saucers!