Is it OK to turn off O2 in Rebreather Training?

[doctormike]

So, lesson learnt, almost the hard way. And one that I carried over when I became a 'technical' instructor. That is I would announce what drill/s we would do / what 'emergency' may take place pre-dive, but not when. (And so yes, back to the topic at hand, I still think turning off someones o2 unannounced, especially to a student on a re-breather, is asinine!)

So to answer the 'question' posed - Is it unexpected when it is briefed? - yes it can be if the drill is made aware of pre-dive, but not when it may / will take place during the dive. That way then keeps em' on their toes the whole dive.

That's a scary story, but I don't see how it relates to the teaching technique of turning off the O2 of a student without telling them ahead of time that you are going to do it.

I'm not an instructor, and you are, so I respect your experience. But I have to disagree with you on this point.

Telling a student that at some point in the dive you will turn off their O2 completely eliminates the value of this teaching method. If they know it is coming, they will be watching for it. The whole point is that the student needs to experience the reality of a major cause of rebreather accidents in a controlled situation, where the instructor has plenty of time to fix it if the student doesn't pick up on what is happening. You are teaching the student to be aware of this problem, not just how to turn the O2 back on.

In fact, doing this drill might prevent accidents like this one - which was the accident that originally started the thread that this one branched off from:

Ashley Porsche Bugge

 

[Superlyte27]

Wow, I just read that post by Ashley. I pretty thankful and amazed at the willingness to post the black box and the events leading to the death. I’m also thankful that the Liberty has the black box. I’m also thankful that the Liberty’s handsets both vibrate when the PPO2 drops to a dangerous level. It’s obnoxious and can’t be ignored. You certainly know it when it’s happening. But now am painfully aware that if your oxygen isn’t turned on, and you’re in surface mode, you’re probably already dead by the time the handsets start to vibrate if it happens at the surface. FYI, I am a Liberty Instructor and prefer the unit over several other units I’m certified on.

I have a few questions, probably rhetorical, I doubt I would ever ask her.

1. How long had he been diving a rebreather prior to taking that trimix class. I ask this because there comes a point where you assume the diver knows what he’s doing. If I’m teaching a Trimix class, I’m not watching to make sure you packed your scrubber right. You should have substantial hours on your unit at this point. I do think I’ll be double checking to confirm everyone’s friggin oxygen is on now. I believe I ask this prior to every dive now... but I’ll be certain for sure.

2. And this is for other instructors... Are you guys letting students bring cameras to class? I have never allowed it for exactly this reason; too much task loading.

It’s a sad situation. It sucks when people die for stupid reasons. This and most CCR deaths are easily avoidable.

 

[JohnnyC]

I do think I’ll be double checking to confirm everyone’s friggin oxygen is on now. I believe I ask this prior to every dive now... but I’ll be certain for sure.

I have a pretty firm policy of a challenge and response procedure of "gas is on" and I expect the same in return. If my buddy isn't ready, I wait and do it again.

I'm also a firm believer in a solid pre-breathe in order to double-triple-quadruple check function of the unit. If you're pre-breathing a unit then turning it off, you're not pre-breathing it. Simple stuff like this saves lives. There's a reason we do it. Getting sloppy can be disastrous.

And I have NEVER taken a camera on a training dive where there are skills expectations to be met. Camera for some rinky dink PADI underwater fish barista distinctive specialty, sure, but if you have to perform, ESPECIALLY on CCR, I would never even consider it as an option.

 

[doctormike]

I'm also a firm believer in a solid pre-breathe in order to double-triple-quadruple check function of the unit. If you're pre-breathing a unit then turning it off, you're not pre-breathing it. Simple stuff like this saves lives. There's a reason we do it. Getting sloppy can be disastrous.

Exactly. And the pre-splash checklist should be one after you have donned the unit. Doing it before you put the unit on puts you at risk for missing stuff like valve roll-of, LP feed disconnection, etc... And it should include a full pre-breathe, in the unit, watching to see if it holds your setpoint. The pre-breathe isn't just for CO2 (not clear that it even can always pick up breakthrough).

 

[Superlyte27]

I have a video of a friend testing this on my couch. Friendly environment, no class setting, no payment involved, I wasn’t even his rebreather instructor.

Breathing a purposely mis-packed scrubber, in less than two minutes it looked like he was suffering from a heart attack. No way to self rescue.

Now, this isn’t empirical by any means, and probably not even accurately duplicated. Who’s to say breakthru is possible, but not so bad that it would show up in the first 5 minutes...

I trust my scrubber. I trust my packing abilities. I’m doing a pre-breathe to test everything else more than “activating the sorb” or testing for breakthru.

And guys, do this on land. As I said in another thread...
It’s really common to pre-breath in 4’ of water while you’re hooking up bailout. Passing out at a picnic table isn’t fatal. I have seen two friends pass out in 4’ of water. If not for a stranger noticing what was going on, both of my friends would likely be dead. (I wasn’t their instructor either).

 

[Kay Dee]

That's a scary story, but I don't see how it relates to the teaching technique of turning off the O2 of a student without telling them ahead of time that you are going to do it.

Obviously you did not read / think about my last sentence i.e.

...........................And so yes, back to the topic at hand, I still think turning off someones o2 unannounced, especially to a student on a re-breather, is asinine!

 

[Kay Dee]

Telling a student that at some point in the dive you will turn off their O2 completely eliminates the value of this teaching method.

Not that I'd do it but..................B****s**t! With all due respect, IMHO, you do not know of which you speak.

 

[Kay Dee]

And I have NEVER taken a camera on a training dive where there are skills expectations to be met.

EXACTLY!

Camera for some rinky dink PADI underwater fish barista distinctive specialty, sure, but if you have to perform, ESPECIALLY on CCR, I would never even consider it as an option.

Well, not quite, but..................certainly not on ANYTHING other than a specific photographic (handling) training dive, whether on OC or CCR.

 

[Kay Dee]

I trust my scrubber. I trust my packing abilities....................................

Exactly re now underlined, although in 12 years of CCR diving, most of it deep, or even very deep, and thousands of hours on CCR, I never pre-breathed my scrubber. Make of that what you will, given the (now) underlined. But after, all I dived a Mk-15.5 and after all "I trust my scrubber. I trust my packing abilities". IMHO, say no more.

Now I ain't telling anyone what do to by any means, just what I and others did.

And I do not care one iota what anyone thinks about that 'non-practice', ALL my students are still alive, almost 20 odd years on. (Well, 'cept one who died when he crashed his plane, but I can't be held responsible for that. )

 

[doctormike]

Obviously you did not read / think about my last sentence i.e.....

Not that I'd do it but..................B****s**t! With all due respect, IMHO, you do not know of which you speak.

My post was in response to your last sentence, which I did read and think about.

Hey, maybe you don't agree with me, that's fine. But try to understand what I'm saying. Tell me without resorting to profanity what you think is wrong with this teaching method.

What is good about it is that it requires the student to actually respond to one of the most dangerous failure modes in CCR diving. The student needs to RECOGNIZE what is happening when it happens. If you are told it's going to happen, you don't get that experience or training. If you have a counterargument other than "it's asinine and BS", I would like to hear it.

If you read upthread you will see the discussion of the objections to this method and the responses from people who support it. I'm interested in YOUR objection to the method. We do other training procedures that have some risk associated with them (bailout ascent with a deco obligation, loop recovery drills, etc..). So tell me why you think that it's so dangerous. Yeah, there was a death in cave training that was cited, but that was not this. That student was blinded and couldn't see the PO2 reading. Completely different thing.

The instructor turns off the student's O2, and watches the student's PO2. If it drops to, say, 0.7 without the student noticing it, the instructor turns it back on and fails the student. The main risk that I see is if (1) the student doesn't notice the PO2 dropping, (2) the instructor dies or otherwise becomes incapacitated, and (3) the student doesn't notice the low PO2 alarms eventually going off. Is that the scenario of concern?