Ascending without BC's deflation / inflation

[Pliny]

Pliny that would have made me nervous as hell. My understanding is that you cannot feel an embolism as you have no nerves in your lungs. I'm look forward to your response on this TSandM. Is there any way to tell if you are in danger of an embolism from feeling?

The fact gas was escaping puts some limit on the overpressure in the lungs. I was at about 25' and rose maybe 2 feet in the course of the inhalation to get over a coral head so the ascent rate was normal. Computer didn't beep.

Remember we used to ascend by what would now be considerered cesa. Re your buddy who was ascending out of control you probably had a greater margin of safety and could have hung on. I can't fault you as I wasn't there though.

 

[TSandM]

As long as your glottis is open (and it will be, if you are moving air) then you won't suffer an overexpansion injury unless you have pathology in your lungs (which is why we worry about people with prior lung injuries, or with asthma). To feel the difference between an open glottis and a closed one, as you are sitting there, try inhaling very, very gently. Now stop inhaling just for a tiny second, and inhale again -- you're maintaining an open glottis. Now stop inhaling and "hold" your breath. You have closed your glottis -- you can relax your chest muscles, and no air will exit your lungs. THIS is the state that is dangerous when ascending. Your glottis is very powerful, and can hold more pressure in the lungs than the tissue can tolerate. You may or may not feel a lung overexpansion injury -- such types as pneumothoraces can be painful or leave you short of breath, but air embolisms are generally painless (but can be devastating injuries).

If you are doing a swimming ascent, you have to be more or less vertical (more, if you are going up a vertical line). If your buddy, ten feet away, has a problem, you can't swim TOWARD him, because your fins are pointing down. On the other hand, if you are floating up in a horizontal position, you can move forward easily to grasp the line, if need be, or to get to someone to assist them.

The buoyancy control required to do a neutral, horizontal ascent requires practice. Let's face it -- the easiest ascent is hand-over-hand up a line, but that's not always available, and if the surface is rough, it's not a good option at all. Better to practice and develop the skills to make an independent ascent.

 

[h90]

I have usually an empty or almost empty BCD when I ascent (at least I try, depending on the weights of the DC).
Also I like to have a slight negative buoyancy, as it is much easier to control a slow ascent and there is no risk that I get too positive when the air in the BCD gets bigger.

 

[Bubbletrubble]

@markmantei: For the record, I didn't say that a diver conducting a negatively buoyant, kicking ascent would "risk buddy separation." Please re-read my post.

I think that, in principle, the people who have put together the PADI curriculum would agree with you. That's why the final "S" in the S.T.A.R.S. acronym stands for "swim" up the water column while maintaining slightly negative buoyancy.

If you are doing a swimming ascent, you have to be more or less vertical (more, if you are going up a vertical line). If your buddy, ten feet away, has a problem, you can't swim TOWARD him, because your fins are pointing down. On the other hand, if you are floating up in a horizontal position, you can move forward easily to grasp the line, if need be, or to get to someone to assist them.

TSandM points out the value of ascending in unison with your buddy and having the ability to adjust buddy positioning in the horizontal plane. It's a much better way of managing an ascent. Yet another advantage of keeping one's body in a horizontal position during ascent is that more drag is created while moving upward in the water column. This dampens buoyancy adjustments somewhat.

 

[Charlie99]

I find a neutral ascent is much more of a lazy man's ascent -- by being near neutral all the time, it's extremely easy to stop, either for decompression, or to deal with a problem or even just watch something interesting.

Or by strongly exhaling, going back down. Being neutral means you are in control of your dive and your ascent. Finning upward to counteract being negatively buoyant is unecessary work.

Early scuba divers didn't have a BCD and we CAN still dive without one, but life is much easier if you use the right tools in the right way.

My advice to the OP is to learn how to use your BCD.
Dumping all of the air out of your BCD before an ascent is just making a lot of work for yourself. The right way is to stay near neutral throughout the dive.

It seems that a lot of divers do their ascent negatively buoyant for fear of a runaway ascent. I recommend that anybody having this fear try an ascent where they are horizontal, not finning, and are neutrally buoyant with their lungs about half full. If you are in this condition, you should be able to exhale strongly and immediately start descending. That exhale strongly is all you need to keep from a runaway ascent while you dump a bit of air from your BCD.

Once you have the knack of doing a slow, non-finning ascent and hover, you will never go back to finning your way back to the surface.

 

[merxlin]

....................My advice to the OP is to learn how to use your BCD. Dumping all of the air out of your BCD before an ascent is just making a lot of work for yourself. The right way is to stay near neutral throughout the dive.

Lets remember what the OP asked :

I was just wondering if are there any instances when at a certain point in time during an ascent a diver ends up with a completely deflated BC and simply has to swim up? In fact, does anybody happen to know if it would be easier or harder to control your buoyancy by trying to swim up (thrust) your ascent having your BC totally deflated?

He was not advocating nor opposing the practice, just trying to get information about it.

 

[Doc Harry]

When I am diving recreationally (warm water, AL80, 3mm wetsuit), I usually end my dive with a completely empty BC. I ascend with breath control only. If your weight is dialed in correctly, this is very easy to do.

 

[Thalassamania]

This seems a good place to (once again) mention the "air siphon," something I have discussed before. Each BC is a little different so you will need to experiment and practice if you want this in your bag of tricks. It can result in a highly controllable ascent, kinda the best of both worlds:

Start kicking up. When your BC has expanded enough to keep you moving, relax and let it carry you upward. Hold the oral inflator hose as far down (deep) as you are able and keep the oral inflation button OPEN. Continue to keep the oral inflator button open and move the hose up until air starts to trickle out of the oral inflation mouthpiece, then lower it till it just stops. You now have an air siphon from your BC or BP/W that you can use to control your ascent or descent rate with amazing precision. Just remember to keep the oral inflator OPEN ALL THE TIME. THIS TECHNIQUE REQUIRES PRACTICE - try it on some normal ascents first!

 

[captain]

I was just wondering if are there any instances when at a certain point in time during an ascent a diver ends up with a completely deflated BC and simply has to swim up? In fact, does anybody happen to know if it would be easier or harder to control your buoyancy by trying to swim up (thrust) your ascent having your BC totally deflated?

You might like to read this.

http://www.scubaboard.com/forums/vi...32-diving-without-buoyancy-compensator-2.html

 

[markmantei]

This seems a good place to (once again) mention the "air siphon," something I have discussed before. Each BC is a little different so you will need to experiment and practice if you want this in your bag of tricks. It can result in a highly controllable ascent, kinda the best of both worlds:

Start kicking up. When your BC has expanded enough to keep you moving, relax and let it carry you upward. Hold the oral inflator hose as far down (deep) as you are able and keep the oral inflation button OPEN. Continue to keep the oral inflator button open and move the hose up until air starts to trickle out of the oral inflation mouthpiece, then lower it till it just stops. You now have an air siphon from your BC or BP/W that you can use to control your ascent or descent rate with amazing precision. Just remember to keep the oral inflator OPEN ALL THE TIME. THIS TECHNIQUE REQUIRES PRACTICE - try it on some normal ascents first!

Another thing to try in the pool. I know I kind of hijacked the thread, but learned alot and am going to play with both these options. I don't necessarily think the negative assent is an improper way to teach students, and see some advantages in that method, but I also like some of the advantages of the other methods.