How deep is dangerous?

[Neff]

Can anyone tell me, what is the maximum depth before an uncontrolled ascent becomes dangerous ? Last August, I had been using my own BCD with no problems but on the last day of holiday diving, I stupidly used a BCD from the back of a dive schools supply. I confess that I did not test the deflate properly. Yep ..... you've guessed it, it wouldn't. I was only about 14m and slowly rising, trying to let air out of the BCD but it would not deflate. I tried everything I could think of as well as splaying out for drag and exhaling as much as poss before taking in a short breath and exhaling. I could not stop the uncontrolled ascent. unfortunately, I was in mid water and there was nothing to hang onto. Anyway, on surfacing, I waited, checking out if I felt anything different, I didn't. I klept aware of my body for the next 36 hours but I was fine. So .... this is making me think that maybe there is a depth at which these problems begin. Is this true ? . not that I would push my luck ever, but it would be good to know the facts. Can anyone help ?

 

[scarefaceDM]

4 feet. Seriously.

 

[Neff]

Oh Scareface, I guess I was just very very lucky then Eh ?

 

[nereas]

If you panic and hold your breath, like a novice, then you could embolize your lungs within a few feet, probably 1/4th ATA, which equals 8 ft.

As long as you exhale continuously during your rapid ascent, and do not start to hyperventillate (which extends your lungs near maximum capacity) then embolism should not be a problem for your lungs. (Embolism here being defined as rupturing of your aveoli with gas then mingling in your blood supply.)

If you have been on scuba for a significant amount of time, and you have accumulated an inert gas (N2) load in your blood, then embolism in your arterial blood supply becomes an issue due to the inability of your blood to off-gas properly. Nitrox lessens this risk, which is greater with air and with hypo-oxic trimixes. (Embolism here being defined as major bubble formation leading to cerebro-spinal stroke.)

I always test my power inflator and my wing deflator valves whenever I assemble my gear. That should normally be covered in a basic open water course, and again in an advanced open water course during the equipment module. You should always do it, as you found out.

Nice recovery, though. Good thing you kept your head through it all.

 

[300bar]

4 feet sounds about right,could be 3.breath holding that is.

But i guess that was not the question,but more in relation to the depth/divetime.
No expert on this but,one could assume that when we stay well within NDL at 14mtr.
It would not be to dangerous.Would not try this for fun thou.

 

[under water]

Seems to me it depends on a lot of things.
If you hold your breath then 4 feet would be dangerous.
If you just jumped in and have not accumulated any N2 bubbles then it would be less dangerous than at the end of a longish dive.. or a series of them.
If you were in an uncontrolled ascent and a boat was heading your way it would be bad!

 

[Charlie99]

There are two main risks -- barotrauma/AGE and DCS.

A rapid ascent with your airway closed can cause lung damage and arterial gas embolism. Very dangerous and potentially fatal. AGE can happen in relatively shallow water. A rapid ascent could possibly also cause other barotrauma such as problems with sinus or ears if you have a reverse block, but that it not very common. The risk of barotrauma and AGE exists once you have breathed compressed air at depth.

The risk of DCS or bends from a rapid ascent depends on the nitrogen loading, which in turn depends upon both the depth and time at depth. For example, a freediver can rapidly descend to 100'/30m, stay down there a minute or two, and then pop back up to the surface rapidly with little risk of DCS. On the other hand, if you stayed at 100'/30 meters for 15 or 20 minutes and then did a rapid ascent would put you at great risk of DCS. At the 14m/47' depth you were at, your N2 loading is still pretty low for the first 10 minutes are so ---- although DCS is a probabalistic sort of thing -- what turns out OK several times in a row (or with several different people) may end up causing DCS the next time (or to another person).

 

[spectrum]

I think nereas covered it well.

 

[scarefaceDM]

Neff, Yes you were lucky.

Seriously 4 feet is a danger point.

and what nereas said.

 

[300bar]

Oh Scareface, I guess I was just very very lucky then Eh ?

Yes you were very lucky,

If you would have hold your breath,you would have had a nice embolism.
On the otherhand I've tryed this once(yes I know very stupid)holding my breath during a assent.Tryed this from 6 meters upwards.Well I did not made it,it hurst like hell so I had to abandon the effort.:11:
Kids don't try this ever.:no