Breathing from BC

Hi,

Last weekend on a pool dive, I tried breathing from my BC for the first time. Not a necessary skill maybe, but something I wanted to try. Cleaned the bladder out with Scope first and rinsed it.

I started with a little air in the BC (maybe 3 litres). Then I switched from my primary to the BC mouthpiece, pressed the deflate button, exhaled into the BC, then carefully inhaled. It breathed fairly comfortably--like a slightly wet regulator.

But air trickled out around the deflate button. I could slow down the trickle by tilting the mouthpiece so the deflate button was pointed downward. But it continued, especially when I exhaled. After about 6 breaths, the BC was empty, so I switched back to my primary.

This is a Sherwood Silhouette BC. Is it typical for the air to leak out around the deflate this way? Or am I doing this wrong?

The inflator valves shoiuld work so that there's no leakage, not to make breathing off it possible but to ensure effective oral inflation at the surface. If your valve is like my ScubaPro version it needs to be depressed fully to route air from the mouthpiece while closing the exhaust port. Possilby you're not depressing it fully.

As far as breathing off the BC is concerned, it's not a worthwile endeavor, except for the most desperate of emergencies. The inflator hose represents a large dead air space, and the amount of air typically in a BC is pretty small, especially later in a dive when you've vented it to offset the weight of the air consumed from your tank.

Rather than practice a marginal technique, you might focus on better air management to avoid problems in the first place. Besides checking your gas supply more frequently, start thinking of it as minutes remaining, rather than psi remaining. Roughly estimate your rate of consumption by noting the pressure drop over the last 5 minutes or so. Extrapolate that to estimate how long the remaining supply will last, and plan the rest of your dive accordingly knowing how much gas you've reserved for your ascent and safety stop.

IMO divers focus too much on dealing with OOA problems, and not enough on better dive management to avoid them in the first place.

I read you cleaned it out with Scope... still seems like a GREAT way to get a nasty respiratory infection from all the bacteria and crud growing in the bladder. Yuck.

If I understand you correctly, air was coming from between the deflate button stem and inflator housing. That really does not surprize me considering the manual inflate stem on all the BCs that I recall do not seal that stem. No real need to, usually there is water on both sides of it or you are dumping air and any small leakage when orally inflating is not worth trying to save.
However, I agree with Don, it's a skill not worth doing and possibly one that could end up causing you harm from a lung infection. Besides, if you have enought air to breath off of in your BC at any time other than the surface, you are grossly overweighted.

carefully if the BCD is old....I would worry what kind of fungi are in there.

herman:

Besides, if you have enought air to breath off of in your BC at any time other than the surface, you are grossly overweighted.

Click to expand...

Hmmm, that somewhat throws a spanner in the works. I recently tried breathing from my BC in pool (and yes, overweighted for this exercise as otherwise I can't put any air in my BC without becoming buoyant). The reason I tried the exercise was just to have done it, even once, so in the unlikely event of ever needing to perform it, it wouldn't be the first time. No-one gets things right first time. Well I don't at least.

Breathing from the BC could still be viable tho, as you could breath from it while dumping (in a CESA scenario for example).

But it's a good point, if you're correctly weighted you're likely not going to get much out of the BC at the depth you are at when the OOA situation occurs, which I thought could be an option to swim to an otherwise out of reach buddy as an alternative to a CESA.

Back to the drawing board

I also agree that more time should be spent practising good gas managements and buddy skills. But I still want to know which options I have available if the brown stuff really hits the fan. And my BC is new

JClynes:

But it's a good point, if you're correctly weighted you're likely not going to get much out of the BC at the depth you are at when the OOA situation occurs, which I thought could be an option to swim to an otherwise out of reach buddy as an alternative to a CESA.

Click to expand...

I think it would depend on the dive. In cold water, at great depth, the BC will be almost fully inflated as it is making up the difference in buoyancy of a compressed wetsuit. In other cases, it is making up for the weight of air in the tank. For an HP 100, this is about 8#

Richard

JClynes:

.....Back to the drawing board

.....I also agree that more time should be spent practising good gas managements and buddy skills. But I still want to know which options I have available if the brown stuff really hits the fan.

Click to expand...

Try practicing breath hold underwater swimming with fins. You'll be surprised how much range you have both in time and distance. Developing this skill so you're comfortable with it will stand you better than your BC.

It isn't running out of air that'll kill you, it's the panic of not having a plan or knowing that you have time to swim to a buddy (or reasonably slowly to the surface, if that's an option).

don Francisco:

It isn't running out of air that'll kill you, it's the panic of not having a plan or knowing that you have time to swim to a buddy (or reasonably slowly to the surface, if that's an option).

Click to expand...

Agree entirely. Hence why I'm keen to familiarise myself with all possible options and to simulate the situations. I was actually getting so comfortable with the OOA situation that I recently forgot to replace my reg after a drill Complacency, as opposed to panic, can be dangerous too I guess.

don Francisco:

Try practicing breath hold underwater swimming with fins. You'll be surprised how much range you have both in time and distance. Developing this skill so you're comfortable with it will stand you better than your BC.

Click to expand...

Good tip, don't know why I haven't tried that but that's something I'll remedy by this time next week

Cheers!

Back in the day, this was an emergency technique we philosophized about and some of us practiced (see drill below) for egress from caves during a complete disaster dive. What we learned was 1. As far as I know no one has ever successfully used this technique to egress during a real emergency. 2. It is very dangerous, each breath increases the amount of CO2 you are breathing and blackout is a real danger. 3. Sitting at the bottom of the pool and doing this drill is not “real World”. If you were doing this for real, your gas is gone, or damn near gone, your regulator has failed, your buddy is gone, and you are swimming for all you are worth towards the cave entrance. With the amount of work you are doing and the fear you are probably feeling, CO2 is building up rapidly and in a word , you will not make it. If you don’t believe me do this, swim as fast as you can back and forth in the pool, get that SAC rate up, way up, EXHALE and then switch to your BC. Now how many breathes do you get? This is why we gave it up. This is a useless, dangerous skill. This is not taught by any agency I know. This is why we have redundant systems and Buddies in overhead environments and are taught CESA for open water.