Using exhale breath for BC buoyancy

Deac in the Wake · Nov 12, 2009

Obviously when you refine and maintain your buoyancy skills, the amount of air you use in your BC becomes reduced, especially at depth.

So I'm curious if any of the board vets here ever use exhaled breath for BC adjustments or think it's not worth the effort. I can see using it in an exigent situation (e.g. after a CESA or running low/out of tank air on the surface). But I've practiced using exhaled breath even underwater to make minor BC adjustments, mainly to have the skill. But I'm curious if it's worth the trouble. Sure it saves air but how much? Doesn't seem like it would be enough to matter- unless you've had a major "something" happen and a couple of breaths may be the difference. It's breath you'd otherwise blow away and can still be used to inflate.

So what say ye?

DCBC · Nov 12, 2009

Perhaps I don't quite understand what you're getting at. If you exhale into your B.C. to adjust buoyancy, what you have lost in your lungs is transferred into the B.C. bladder; buoyancy doesn't change until you inhale. If you don't have enough left in your lungs to do so, you will use your purge valve (resulting in some pressure loss in your tank). Even if you could save some air by doing this, it's negligible.

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HowardE · Nov 12, 2009

Why take your regulator out of your mouth if you don't have to?

dkktsunami · Nov 12, 2009

It would probably be better to concentrate on making "minor adjustments" not with the bc but with your lungs. Certainly you should have the skill to orally inflate underwater, and it's a good skill to practice, but it's probably not worth the effort as a matter of routine to do this to save a breath or two on every dive. More than likely you are, or soon will be, surfacing with more than a minimum amount of gas anyway. Ideally you want to minimize the number of bc adjustments and make minor depth changes by expanding or contracting your lungs.

paddler3d · Nov 12, 2009

I wouldn't bother trying to maintain your buoyancy under water by adding air to your BC with your exhaled breath vs. using the inflator.

Is you concern that you are trying to conserve your breathing gas?

Teamcasa · Nov 12, 2009

Deac in the Wake:
So I'm curious if any of the board vets here ever use exhaled breath for BC adjustments...

Sure it saves air but how much?

I'm assuming the question is centered around saving/conserving tank air.

For me, the amount of air saved would not be worth the effort.

TSandM · Nov 12, 2009

It's a great skill to practice regularly, so that your brain remains aware of the fact that it is possible.

But you don't save much gas that way, and it's kind of a PITA to do. Properly weighted in a single tank, I only really add gas at the very beginning of a dive, and gradually vent it as I use my gas and get shallower, so there's little need to add gas repeatedly.

Cave Diver · Nov 12, 2009

Deac in the Wake:
Obviously when you refine and maintain your buoyancy skills, the amount of air you use in your BC becomes reduced, especially at depth.

So I'm curious if any of the board vets here ever use exhaled breath for BC adjustments or think it's not worth the effort. I can see using it in an exigent situation (e.g. after a CESA or running low/out of tank air on the surface). But I've practiced using exhaled breath even underwater to make minor BC adjustments, mainly to have the skill. But I'm curious if it's worth the trouble. Sure it saves air but how much? Doesn't seem like it would be enough to matter- unless you've had a major "something" happen and a couple of breaths may be the difference. It's breath you'd otherwise blow away and can still be used to inflate.

So what say ye?

Yes. I typically do it on descents to keep up with the diminishing volume of the wing from added depth.

HowardE:
Why take your regulator out of your mouth if you don't have to?

It's a skill and like any other skill, I like to periodically practice it. If on OC, it helps get a feel for how much air you can exhale and still sufficiently clear a reg and it's also helps keep me comfortable with reg switching. Spending time with a reg out of my mouth in a controlled situation reduces the stress of this action if I ever find myself in an uncontrolled one.

On CCR, I don't do it as much, but I still do it some. It helps build muscle memory for closing the loop when switching to bailout.

Gombessa · Nov 12, 2009

A minor point - over the course of a long dive, I imagine that the amount of water building up in the BC bladder from doing this would reach a "mildly annoying" level. Not that it would significantly impact the lift of the wing, but when you'd notice it afterwards when you're tearing down your gear

wxboy911 · Nov 12, 2009

When I shore dive I fill my BC manually before I enter the water-Honestly it probably makes little difference but I feel like I am saving my tank air for the dive. When at depth I won't take the 2nd stage out of my mouth unless I have a good reason.

Using exhale breath for BC buoyancy

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