Why is inhaling while ascending safe, if breathing holding will cause lung over expansion?

[Nitrox_DiverNY]

No, I don’t think it’s common practice, but it is a good practice. That last part of the ascent is going to be where you are most buoyant. Any air in compressible vessels will be at near surface volume, so exhaling can help to slow the ascent in those last few feet as well as making sure the airway is open.

I don’t think it’s common practice because I don’t think the expansion rate is well understood among recreational divers. I’ve seen people on here unclear that the greatest risk of lung over expansion is near the surface. And that’s from people on SB, who I would guess to be at least inquisitive about diving. The vast majority of divers aren’t here, and might not be as curious to dig deeper. They may understand not to hold their breath, but maybe not precisely why, and where it’s most critical.

Thanks for the feedback!

 

[Nitrox_DiverNY]

I have held my breath on ascent while scuba diving a few times (I was super stressed one time and another time I must have thought I was freediving). Anyway, I think if you are healthy and not completely panicked, you will begin to feel a fullness in your lungs and (unless you try otherwise) you will just naturally exhale. Definitely not something to replicate or test, but if you remain reasonably relaxed you should probably be OK. As long as the air way is open, even a little, excess pressure should be vented before it can build up.

Also remember, the expansion rate is not that great until you get really shallow, I just always exhale for the last 3-5 feet, I think.

I found this video, it shows a diver getting an injury. Very interesting I thought. Freediving and breathing compressed air can be dangerous if you forget why your lungs are burning, I guess.

just watched that video, I feel bad for that guy. Those things do look like death traps, but a Very informative video tho and I did subscribe to them

I don't think those air-bells are worth the novelty, kinda stupid if you want to talk go get FFM training and you will be all set to talk the whole dive

 

[Belzelbub]

I don't think those air-bells are worth the novelty, kinda stupid if you want to talk go get FFM training and you will be all set to talk the whole dive

Yeah, I don't get the air bell in that video, but do see the purpose in other instances. I've used one once at Blue Grotto. In that case, we just popped in it for a bit, looked out the windows, and continued the dive. So, mainly a novelty.

They can be useful in some situations for deco, but as the one in the video was right on the bottom, not the case.

On scuba, there is usually no risk of using an air bell, assuming the air inside is safe. You would be breathing at the same pressure from your tank, or in the bell. The air bell in that video just seemed useless. Not very deep, so unlikely for scuba divers to be using. And that's the danger. Freedivers hold their breath on ascent. This is safe as the air is originally at surface pressure. Not the case once he started breathing from the air in the bell.