Breathing off the BC

[Genesis]

Just keep your reg in your mouth and you will find more air as you ascend. You have got to love Boyle's law. Stick to your training... and it will get you through.

That will not be true if a LP hose has blown and bled your tank dry (it may not be true even if the tank isn't dry yet!) and you MAY get water back through the open LP hose connection!

"One size does not fit all when the water turns brown."

 

[cat]

fins wake once bubbled...
Well, most of us don't know how to clean things to surgical standards. But fair enough, if you're going to practice breathing your BCD, use Listerine, iodine or similar. It's better than not using disinfectants.

Ok, I'm going to be really rude here and flat-out contradict something - but it's important and I'm hoping the original poster doesn't mind, as it wasn't the central part of his thesis.

DO NOT use iodine to disinfect your BC, unless you've got one coated in teflon or one of the other ultra-resistant fluorine-containing polymers. Two reasons: 1. iodine (and fellow halogens chlorine and bromine) EATS polymers, especially flexible ones - the bladder will lose flexibility and become brittle. 2. iodine is noted for it's ability to migrate into many mterials, especially plastics - you won't get the stuff out again and you don't want to breathe the iodine fumes that may slowly seep out over time. (Note: chloride isn't the problem, chlorine, as in bleach, is.)

Anything exotic (ie disinfectants other than alcohols) going into my BC bladder is getting checked on a polymer compatibility chart first.

You know, NetDoc, this thread IS about breathing the BC. It's not about preventing the OOA. What you are doing looks like hijacking to me - I doubt if any of us were considering this as an alternative to planning a dive, checking gauges, etc - it's a last resort back-up tool. You don't want to consider the 0.0001% or whatever number you've assigned? Fine. Just please don't try to prevent others from doing so.

I've worked with hydrofluoric acid (not right now, thank goodness). It's freaking dangerous stuff - spill some on yourself and it can sink through your skin and screw up your internal Ca2+ balance (which will likely kill you in a horrible and painful way) - and start eating your bones (if you aren't dead already). I wear doubled gloves, heavy apron, safety googles, handle it in a hood, plan carefully, dispose of correctly and all that (training, experience, correct equipment). If I pay attention, I will not spill any HF. Ever. And only a real dumbass would ever spill any on their bare skin, right? There's gloves and apron and all that in between me and the acid. So why do labs that use HF have calcium gluconate gel patches available in case someone does spill HF on their skin?

Because... they can buy critical time to get someone to a hospital if the worst happens and some HF does reach the skin. I *won't* work with HF unless there's some in the lab, even though I've never spilled any on my own skin or personally know anyone who did so. I don't even know if the patches have saved anyone's life (hard to run a controlled experiment on that sort of thing) I certainly wouldn't respect or listen to anyone, no matter how senior or experienced a chemist, who told me I shouldn't bother with having the patches around because it was highly unlikely they'd be needed...

I'd also kick someone out of the lab if I thought they were getting careless with HF because the patches were available.

IS this making any sense?

Sorry for the extended analogy - couldn't see any other way to make my point. Cheers, all.

 

[fins wake]

That will not be true if a LP hose has blown and bled your tank dry

LP hose blowouts are extremely rare occurences and almost invariably happen when you first switch on the gas at the surface. In the highly unlikely event of an LP hose blowout under water you'll have a few minutes to get up to the surface. If there's any water coming through you might choose to inhale by pressing the purge button and holding the 2nd stage some distance from your mouth.

Oh. I see. Since it hasn't happened to you, it doesn't happen? Brilliant!

Hasn't happened to me either. In fact, no diver I've dived with has ever experienced an OOA ... funny that, eh? (Hint: I'm a good buddy. SPG:s are there to be used ...)

When you are in the water, you are on your own.

Not really. You've got your buddy. You've also got your training, based on the standards of your agency. For an autodidactic solo diver your premise might be true. Otherwise not.

There are many cures for respitory infection.

Well, run this by the docs and see what they say.

There are none for drowning.

And well-trained and attentive divers keeping their equipment in order and diving with equally attentive buddies won't drown on an OW dive within NDL limits. I dare you to show me one (1) instant where this has happened. Go on! Show me!

In fact, we've gone out of our way to ecludiate the fact that no training agency prohibits anything once you're certified.

It's a free world. Well, for some, at least. But the diving agencies won't condone your behaviour either. And they strongly discourage practices which are against their standard.

Translate: You're too dumb to figure it out.

Speak for yourself.

 

[fins wake]

DO NOT use iodine to disinfect your BC, unless you've got one coated in teflon or one of the other ultra-resistant fluorine-containing polymers. Two reasons: 1. iodine (and fellow halogens chlorine and bromine) EATS polymers, especially flexible ones - the bladder will lose flexibility and become brittle. 2. iodine is noted for it's ability to migrate into many mterials, especially plastics - you won't get the stuff out again and you don't want to breathe the iodine fumes that may slowly seep out over time. (Note: chloride isn't the problem, chlorine, as in bleach, is.)

Fair enough point. I stand corrected on this one. (I do know of some guys using iodine in their BCD:s, so I'll pass this on.)

You know, NetDoc, this thread IS about breathing the BC. It's not about preventing the OOA.

With all due respect, Cat, you're allowing your inexperience to show here. It is about preventing the OOA. Had this thread been about using the two-three breaths one could reasonably expect to safely use on one's way up from a depth and time-frame well within NDL limits to the surface (e.g. from 30 metres/100 feet) then I wouldn't have many objections, and I doubt if NetDoc or anybody else would either.

So let's consider the hijack scenario: We've been run through cave deaths (waaaaay inside, and not OOA:s by all accounts), we've been run through getting caught in kelp and wrecks (what the heck are OW divers doing down there without redundancy and training?!?) and all kinds of other issues. The only scenario missing by now are the little green men from Mars turning up at great depth and stealing your tank (presumably for scientific studies) but leaving you with your BCD ...

We've also been told - repeatedly - that hypoxia and hypercapnia will leave you but with a minor headache. This completely ignores the fact that breathing in and out of your BCD - not exhaling into the water - will make your BCD a rebreather (!), and by far the greatest number of rebreather deaths are due to hypoxia and hypercapnia. And this BCD rebreather has no scrubber. Nor does it have ways of automatically filling your bladder with fresh diluent gas.

Under the circumstances, NetDoc is not hijacking the thread, he is putting things into their proper perspective and focussing the readers on the real issues at hand: avoiding the OOA in the first place. And I still haven't seen a single example brought forward of trained, attentive dive buddies experiencing an OOA ... Come on, where are these myriad OOA:s happening out of the blue at the whim of Mr Murphy to the best of us?

 

[JeffG]

fins wake once bubbled...
<snip>With all due respect, Cat, you're allowing your inexperience to show here. It is about preventing the OOA. Had this thread been about using the two-three breaths one could reasonably expect to safely use on one's way up from a depth and time-frame well within NDL limits to the surface (e.g. from 30 metres/100 feet) then I wouldn't have many objections, and I doubt if NetDoc or anybody else would either.
<snip>

With all due respect Fins Wake, thats exactly what this thread was about.

NetDoc's case was that all OOA's are preventable by the diver. Other people thought that Murphy can/could play a part. Popeye's case is that he will do anything in his power to survive, and also that all divers should make their own decision about what/how they train for emergencies.

Your case....You jumped around allot. You basic case was, if the solution is not in the manual, then it shouldn't be done.

Jeff

 

[Genesis]

LP hose blowouts are extremely rare occurences and almost invariably happen when you first switch on the gas at the surface. In the highly unlikely event of an LP hose blowout under water you'll have a few minutes to get up to the surface. If there's any water coming through you might choose to inhale by pressing the purge button and holding the 2nd stage some distance from your mouth.

A "few minutes"?

Please do the test I recommended earlier for you non-believers in how fast a blown LP hose will dump a tank - take the LP hose off your regulator, so its open at the end, jack the reg to a tank, SECURE THE HOSE so it doesn't whip around and hurt you, and open the valve fully.

Be prepared for a lot of noise, and note the pressure gauge and how quickly that SPG moves in the "oh cra%!" direction.

Time it if you'd like.

While it is roaring, take your OTHER regulator (the one still attached, right?) and attempt to breathe off it. You will find it to be VERY difficult to do so. In a stress situation (and trust me, when the hose breaks you WILL be stressed!) you may as well have NO air available - even though the tank pressure is there until it bleeds down.

The problem is that the IP in the hose at that point is very nearly zero, and without IP your reg won't work right. You CAN inhale against this, but it won't be easy, and you won't get much air. For a simulation of exactly how hard it will be, unplug your first stage and attempt to inhale through it with the reg not attached to a tank. Its possible, but if you think you'll get anything approaching a real breath off it you're smoking some really good stuff.

An LP hose failure is very close to a "worst case" scenario underwater. Just about the only thing worse is a complete 1st stage lock-up.

 

[fins wake]

NetDoc's case was that all OOA's are preventable by the diver.

And he's right, and that's easily the most constructive and useful piece of advice from this whole rather sad thread.

Other people thought that Murphy can/could play a part.

Which you can't prepare for? Nah! The only 'Act of God' diver death I know of - and the only OOA dive fatality where the diver was entirely blameless - was the tragic death of Parker Turner. I know of no other, and this was a caving accident (albeit a freak one), not an OW one.

Popeye's case is that he will do anything in his power to survive,

... apart from diving with a qualified buddy, using redundant air sources, or even breathing into the water if using the BCD.

and also that all divers should make their own decision about what/how they train for emergencies.

Sure, do as you like. It's a free country, and there is no scuba police. If you feel newbie divers should discard what all diver training agencies actually prepare and train for, go ahead. But be prepared to see those diving incident and accident figures go up, not down.

Your case....You jumped around allot. You basic case was, if the solution is not in the manual, then it shouldn't be done.

No. Read my threads again, they're completely consistent from the first to the last one:

(1) I would strongly discourage newbies from practising BCD breathing.

(2) I agree with NetDoc that a properly trained diver, keeping his equipment in order and diving with a similarly skilled buddy, will have basically zero chance of an OOA. And no-one has come forward with even a single example of this occuring in real life. LOA:s yes, OOA:s, no. I know of OOA:s but they've happened to dive morons who've completely forgot to check their SPG:s and who - quite frankly - are a danger to themselves and to their dive buddies.

(3) If for some moronic reason (because it will be a diver competence issue!) you end up breathing from your BCD, you should take only a few breaths, exhale into the water and get the heck to the surface finning like mad. Point.

Once you're on to BCD breathing, you're really in big trouble! Big trouble! It is something to be avoided at all costs, and the time and effort required to clean your BCD, practice the drills and do so in safety is better spent ensuring you have the redundancy, training and buddy skills to get out of virtually any situation alive.

If I'm getting a bit irate, it's because the level of the "opposition" argument is very low indeed, even descending to such blatantly silly comments that breathing from a rebreather such as a Momsen Lung is similar to a BCD. No, it is not! The BCD lacks a scrubber! (And I'm not even onto things like ADV:s yet ... you will go increasingly hypoxic in the shallows.)

I know there is considerably rebreather ignorance in the U.S. recreational dive community in particular (and in great swanks of the technical community as well, unfortunately), but please ... There has to be some limit.

Now onto more relevant points:

The problem is that the IP in the hose at that point is very nearly zero, and without IP your reg won't work right. You CAN inhale against this, but it won't be easy, and you won't get much air.

That's right, which is why you need to ascend as fast as you can. The reduction in ambient pressure will make breathing a little bit easier. But again, I stand by my guns. LP hose blowouts at depth are extremely uncommon. I've never seen one in any incident report, ever! (LP hose blowouts on dive boats have occurred rather more often, however.)

As for the timescale inherent in catastrophic gas failure at depth, you will almost invariably have time to

(a) swim to your buddy and get his octo or
(b) swim to the surface.

You can easily do the surface from 30 metres (provided you don't have a blown BCD, which invalidates this thread anyway) in under a minute, if you have to. I don't recommend it, but there it is. And that is the true alternative to drowning ...

I really find most of the counter-arguments in this thread of the "What if the Martians nick my regulator at depth"-variety. I'm not saying even that could never happen (statistically) but it is extreeeeeemely unlikely.

Meanwhile, there might be the odd dozen or more newbie readers of this forum going out practising their BCD skills. I hope I don't have to read about it later in "Lessons for Life" ...

EDIT: minor typos.

 

[Genesis]

quote:
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The problem is that the IP in the hose at that point is very nearly zero, and without IP your reg won't work right. You CAN inhale against this, but it won't be easy, and you won't get much air.
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That's right, which is why you need to ascend as fast as you can. The reduction in ambient pressure will make breathing a little bit easier.

Not at all true. Reduction in ambient pressure will do nothing for you in this instance; the same ambient pressure bears on the open LP hose end and the diaphram of the reg. The change in differential between the two will be zero with changes in depth.

 

[The Chairman]

Uh... this thread was split off of another thread... cuz it had hijacked that thread. It's really a continuation of the earlier discussion. There is no way for you to have known that, but a hijacker I am not. The name was selected at random as it was split with the first half dozen or so posts. Anything covered in those first posts are really fair game to discuss in this thread.

I don't disagree with anyone fighting/doing anything to stay alive but there are limits. I truly believe that there is more usuable air in your tank than in your bladder. The training offered by the agencies is far more useful and natural than most anything else that I have heard presented. However, the best ESA is the one that never happens.

Popeye has actually contended more that I was out to "crush" his idea and thus cause the demise of many air starved divers. The elitist divers he referred to were only out to stop free thinking and make all others subject to our whims about what is right or wrong. Others have questioned how I could be so callous as to believe that many divers have actually chosen to die. In the previous thread it was determined that I felt that my students could commit no error. Now, I live in a fantasy world where OOAs never happen, and I have no business teaching scuba because I do not adhere to the bladder breathing argument. I have actually twisted their words here far less than they have mine... but I did it to make a point. Irregardless of what others might say... I am more interested in diver safety than anything else and probably more than most people. Heck, that’s why I teach teenagers how to dive for free! That’s why I keep diving with them so they can learn even more! Honestly, my megalomaniacal tendencies are highly exaggerated at best! :tease:

Let me put it in yet another perspective... if someone who is completely healthy were to come to me and ask me how to get rid of AIDs how should I answer? Tell them to take this cocktail of drugs and that they will still probably die? Or knowing that they have not yet been infected, do I really and strongly convince them how to avoid it completely? When I point out that many who practice unsafe sex have simply chosen to die by their indecision, am I a pariah? In trying to save others the agony of making bad mistakes, I will surely point out the failures of others and the results. Not in meanness, but with the hope of waking the living up. Now I know this analogy has its limits and I won't push it any further but...

All of you are breathing...
All of you will be making decisions about how you dive...
I want all of you to have safe and happy dives without putting you through needless ESAs...
Consequently, I am preaching the gospel of safe scuba. Plan for and stay within the three limits: Depth/Time/Air, and by all means stay with your buddy. To have a great buddy, you must be one!

 

[Buzcutt]

Genesis once bubbled...
Rebreathing the wing is exactly like breathing on a rebreather - it has ZERO effect on your buoyancy, because the gas volume carried does not change.

Absolutely.

When you breathe off your OC scuba set your buoyancy changes - up and down a bit - with your breathing cycle. This is one of the reasons that nailing buoyancy control for neutrality is such a pain in the butt for new divers - until you get "in the zone" with it, and it becomes automatic, you can and WILL overshoot first in one direction than the other, not realizing that (1) it takes time you to start to move in the water column, and (2) its the AVERAGE of your lung volume, assuming you're breathing in and out regularly, that determines your buoyancy point.


One aspect of buoyancy variation due to breathing is that you change the volume of your displacement in the water as your chest and abdomen expand and contract.