Is it OK to turn off O2 in Rebreather Training?

[doctormike]

Well, the obvious argument to that is not to tell the student that their valve is closed, but rather that their PO2 is dropping. Or even tell them what the lights in the HUD are doing. Student still has to work through the problem, but isn't in actual increased danger. TDI even makes a little prompt slate for just such a teaching moment so you don't even have to write it down. If the student is in enough of a task loaded state, it will result in plenty of thought processes being tested.

-Chris

But there really is a difference between getting a card flashed at you and then going through a memorized drill that you were told was going to happen, and actually having the experience of your PO2 dropping on all three cells, in real time. For one thing, it wasn't until I did that that I really appreciated how slowly PO2 drops with no O2 inputs, and what it actually looks like if it ever happens for real, and what it looks like to fix it.

There is a reason why airlines spend millions on very accurate simulators and don't just tell the pilots that their altitude is dropping. Now I guess the answer to that from your point of view is that they use simulators instead of stalling an actual airplane (TBH, I don't know if they do that or not).

But all I'm trying to say is that this teaching tool was very effective for me and a lot more of a learning experience than just looking at a cue card that I knew was coming. If the CCR instructors here tell me that it's so dangerous that the risks outweigh the benefits, then I should believe them. But since it takes more than 5 minutes for the PO2 to drop to hypoxia, and since the instructor can clearly see the controller and turn the valve in a second, it seems that this could be done with acceptable safety. And I'm probably wrong.

 

[rjack321]

But there really is a difference between getting a card flashed at you and then going through a memorized drill that you were told was going to happen, and actually having the experience of your PO2 dropping on all three cells, in real time. For one thing, it wasn't until I did that that I really appreciated how slowly PO2 drops with no O2 inputs, and what it actually looks like if it ever happens for real, and what it looks like to fix it.

There is a reason why airlines spend millions on very accurate simulators and don't just tell the pilots that their altitude is dropping. Now I guess the answer to that from your point of view is that they use simulators instead of stalling an actual airplane (TBH, I don't know if they do that or not).

But all I'm trying to say is that this teaching tool was very effective for me and a lot more of a learning experience than just looking at a cue card that I knew was coming. If the CCR instructors here tell me that it's so dangerous that the risks outweigh the benefits, then I should believe them. But since it takes more than 5 minutes for the PO2 to drop to hypoxia, and since the instructor can clearly see the controller and turn the valve in a second, it seems that this could be done with acceptable safety. And I'm probably wrong.

OI

I just did a crossover to a mCCR (I was originally certified on eCCR). Sure I had never dove with my O2 off in an eCCR. But I had dove it manually at 1.2 with a parachute SP of 0.7 or 1.0. So you didn't need to shut off my O2 to "teach" me roughly how slowly it drops at a constant depth.

I shut down my O2 on mCCR all the darn time. Diving 32% dil in a cave its almost a necessity to help breath down the loop a little. Nobody needed to shut it down unknown to me to "teach" me how it does/doesn't decline.

This particular accident has happened every few years. Surface hypoxia due to a leaky ADV, shut off O2, or task loading from some other factor like swimming to a tag line etc is dangerous and having experienced shut off O2 at depth is nothing like the ADV diver article suggests. There are ALOT more O2 molecules and fO2 drops much slower at even 2ATA compared to the surface. The drop is slower still at 4ATA since there are basically 4x as many O2 molecules in a given loop volume to metabolize. On the surface with O2 shut off or a leaky ADV you don't have 6 minutes of O2 in the loop.

 

[Superlyte27]

without any instr names what agencies are the instructors you know that are shutting off gas certifying with?

NSSCDS, IANTD, TDI

 

[Superlyte27]

Are you kidding? After this thread? Try Superlyte, maybe he will give up his sources...

I don't see an issue with it. I know in the first 10 minutes of class if my student is an idiot. If he is, more than likely he'll never make it to this point any way.

I'm also very selective in who I'll teach. I make lots of money in my real job, so if you don't have your crap together, it's doubtful I'll take you on anyway.

Lastly, if you suck as an instructor, cerich is right in that you shouldn't be doing this drill this way. Your distraction might kill someone. Thankfully, I don't suck as an instructor.

 

[doctormike]

I just did a crossover to a mCCR (I was originally certified on eCCR). Sure I had never dove with my O2 off in an eCCR. But I had dove it manually at 1.2 with a parachute SP of 0.7 or 1.0. So you didn't need to shut off my O2 to "teach" me roughly how slowly it drops at a constant depth.

Doing it yourself (i.e. switching to low setpoint) is very different than it happening to you unannounced.

This particular accident has happened every few years. Surface hypoxia due to a leaky ADV, shut off O2, or task loading from some other factor like swimming to a tag line etc is dangerous

That's exactly my point. Wouldn't it be better to have a student deal with this exact problem with an instructor right there to turn on the O2 if necessary, than to have it happen for the first time with no one watching?

 

[rjack321]

Doing it yourself (i.e. switching to low setpoint) is very different than it happening to you unannounced.

That's exactly my point. Wouldn't it be better to have a student deal with this exact problem with an instructor right there to turn on the O2 if necessary, than to have it happen for the first time with no one watching?

You can go hypoxic on the surface even with your O2 ON! And the loop can drop out of their mouth and they can aspirate water leading to a life threatening lung infection even if the instructor turns on their O2 but they don't revive/awaken fast enough.

Seriously this is a terrible idea "testing" students with a loop/machine that does not support life - unless its on the couch/picnic table I'm saying no bloody way.

 

[rjack321]

NSSCDS, IANTD, TDI

NSS-CDS: never shut off any of my gas in CCR cave crossover
TDI: never shut off any gas in MOD1
Don't know about IANTD

 

[doctormike]

You can go hypoxic on the surface even with your O2 ON! And the loop can drop out of their mouth and they can aspirate water leading to a life threatening lung infection even if the instructor turns on their O2 but they don't revive/awaken fast enough.

Seriously this is a terrible idea "testing" students with a loop/machine that does not support life - unless its on the couch/picnic table I'm saying no bloody way.

I think that we have been around this particular point many times, I'm not sure what the point is of misrepresenting this teaching practice. Of course I'm not suggesting that the instructor waits until someone becomes hypoxic to turn on the O2 to "revive" them. I'm a newbie rebreather diver, but I'm not an idiot.

 

[Superlyte27]

Let's look at another drill that to me is scarier.

Let me preface this by saying that I do all drills on land. Then the drill is done in open water at about ten feet deep. Then cavern, then cave. If it's not mastered at the basic level, you never progress to the next level of diving. Prior to mastery, they are told the drill is coming. Once they've demonstrated good skill, they know that I can pop any drill on any of them at any time without warning.

At this point, I've co-taught with just about every major player in the game (Florida anyway)In that time, I've seen just about everything go wrong at some point in history.

But let's talk about a lights out air share drill in a cave. Think about ALL the things that could go wrong from simple to extreme. I've seen regs past upside down (which don't work sometimes). I've seen divers swim under the gold line, stuck, while the out of air guy keeps swimming, ripping the reg out of his mouth because he forgot to hold on to the hose with his hand, while he fumbled at first to find the long hose in the dark, then giving up and grabbing his necklace. I've seen gas switches in sidemount that left regs so tangled that when a drill was signaled the OOA diver couldn't get a reg from his buddy. I've seen so many divers mentally and physically unplugged at depth for nearly 10 minutes straight that I was FOR SURE the IT was setting me up. None of them were.

Honestly, you get used to hearing that click of safety from the solenoid. Most new (good)students are so acutely aware of their handset and that oxygen firing that they find it in less than three minutes. And if you as an instructor can't pay attention for three minutes to see if the student catches the drill, you need to quit instructing.

But what do I know? 95% of my students are still diving after nearly a decade and I haven't had a single fatality at any level.

 

[Superlyte27]

NSS-CDS: never shut off any of my gas in CCR cave crossover
TDI: never shut off any gas in MOD1
Don't know about IANTD

We obviously didn't have the same instructors.