Is it OK to turn off O2 in Rebreather Training?

[doctormike]

They started at 0.7
As illustrated with air dil and no O2 its a lot less time. Squirt 10/50 dil in there and you don't have 6 minutes at all, its already hypoxic. Unless I missed it, we don't know the dil this young man was even diving so saying he had XYZ time to respond to his O2 being off (assuming that might be what happened) is misleading.

I think that we are getting two different things confused. I haven't been talking about the OP for a while, I was responding to those who said that my MOD1 O2 shutoff drill was dangerous. To recap, at high setpoint at depth, O2 shut off, student has to recognize this, work out what the problem is and fix it. This was MOD1, so no hypoxic dil, but not sure that would change things the way the drill was done anyway.

From what I can tell, the deceased was doing a trimix class, possibly hypoxic dil, was alone and found with the loop out at 30 feet. That's not what my drill was meant to simulate.

And if that student corks while their O2 is off? MOD1 students aren't known for stellar buoyancy. Swimming along and having the ppO2 drop from 1.2 to 0.7 is nothing like getting in with O2 off.

Exactly, it's a different thing. That has been my point in the past few posts. The drill simulates O2 loss at depth while flying an eCCR on auto.

Loop recovery skills are not done midwater for this exact reason. So that a failed recover leading to a flooding unit, lungs compressing, ear drums popping and not getting to an OC regulator isn't overwhelming students to the point of panic. They settle to the bottom, eventually get OC gas from BO or the instructor, then head up.

Right. So you are OK with the instructor rescuing them in that situation, but not by turning their O2 back on when they haven't even realized that there was a problem.

 

[rjack321]

I think that we are getting two different things confused. I haven't been talking about the OP for a while, I was responding to those who said that my MOD1 O2 shutoff drill was dangerous. To recap, at high setpoint at depth, O2 shut off, student has to recognize this, work out what the problem is and fix it. This was MOD1, so no hypoxic dil, but not sure that would change things the way the drill was done anyway.

From what I can tell, the deceased was doing a trimix class, possibly hypoxic dil, was alone and found with the loop out at 30 feet. That's not what my drill was meant to simulate..

I don't care if you swim around on the bottom with your O2 off and the instructor lets it drop from 1.2 to 0.7 or something before catching you (which seems unlikely unless you go up). Getting IN with O2 off is what kills people. Being on the surface with O2 off is a terrible idea. "Simulating" that is stupid (and probably against standards).

I would not say that a student who fails to recover a loop is in need of rescuing yet. Depends on the student. On some units if the loop falls out there is no recovery, its dead, flooded, done. On others it can float out there open for a long time and still be usable afterwards.

 

[sea_ledford]

Why all of this drama about court? It's such a straw man argument. Yes, I agree with you that the instructor should not turn off the O2 and then continue the simulation until the student is dead.

I do see your point, and I understand that it is not really all that risky to shut off someones O2 while at depth in a controlled training environment. I'm just saying I don't think it actually teaches anything that can't be done in a safer or lower liability method.

I wasn't being dramatic about court, we are having this discussion in a thread about a fatality in a class. You can bet your ass it will end up in court. And staying out of court is a significant part of how course standards are set. You are proposing that an instructor turns off the divers O2, and then turns it back on again after the student doesn't notice. My question is at what point is it considered a "fail"? You say at 0.7, then what is the point of turning it off in the first place? That is when the solenoid will fire. "If your solenoid fires on this dive, you fail." Easy.
If it is less than 0.7, when is the fail? And who decides that? Just because a reasonable instructor would do it at 0.6 or 0.5, it doesn't mean that some numbnuts instructor won't do it at .18.

I run a scientific dive program so maybe I tend to think about the liability aspect more than most, but in my mind training should be about minimizing risks, especially pointless ones regardless of how small the risk is.

 

[Superlyte27]

When I did my cave training, my instructor simply said that if I ever missed my turn pressure, the class would be immediately over, with no refund. That was all it took for me to develop a healthy interest in my relation to turn pressure.​

That's one of the best things Jim ever taught me. I had already been teaching when he started my cave instructor status. I'd set a depth limit of 70' for OW and students would be at 86' on the check out dives. I'd yell and whine, etc, but to no avail. Jim told me to tell them about class being over with no refund. I haven't ever had a student screw that up since. It works for cavern class too. "If you pass the point of cavern, into cave, you fail instantly, class is over, no refunds". It works very well. Thank you Jim W.

 

[Superlyte27]

"Simulating" that is stupid (and probably against standards).

It's not against standards for any of the three agencies I have taught for.

 

[Superlyte27]

I do see your point, and I understand that it is not really all that risky to shut off someones O2 while at depth in a controlled training environment. I'm just saying I don't think it actually teaches anything that can't be done in a safer or lower liability method.

I'm not using it to teach them anything. I'm using it to TEST THEM. It's not for THEIR benefit. It's for mine. It lets me know they aren't complacent about monitoring their gas.

 

[doctormike]

I don't care if you swim around on the bottom with your O2 off and the instructor lets it drop from 1.2 to 0.7 or something before catching you (which seems unlikely unless you go up). Getting IN with O2 off is what kills people. Being on the surface with O2 off is a terrible idea. "Simulating" that is stupid (and probably against standards).

Fair enough. I can't find any post in this thread where someone suggested that.

I would not say that a student who fails to recover a loop is in need of rescuing yet. Depends on the student. On some units if the loop falls out there is no recovery, its dead, flooded, done. On others it can float out there open for a long time and still be usable afterwards.

Right. Exactly the same as a student who has their O2 shut off at depth. They aren't in need of rescue, some might, that's the job of the instructor.

 

[doctormike]

I do see your point, and I understand that it is not really all that risky to shut off someones O2 while at depth in a controlled training environment. I'm just saying I don't think it actually teaches anything that can't be done in a safer or lower liability method.

That's a reasonable difference of opinion. I personally think that the more accurate simulation of the problem you are training for is worth the increased risk, especially since I think that the risk (in the specific context that I have described) has been overstated. It's far safer to not do rebreather training of any sort, but we all do assume a certain degree of risk when we decide to take up this hobby for fun.

My question is at what point is it considered a "fail"? You say at 0.7, then what is the point of turning it off in the first place? That is when the solenoid will fire. "If your solenoid fires on this dive, you fail." Easy.

I don't understand. With what you are proposing, how do you make the PO2 drop? Remember, this isn't the part of the class where you are flying the CCR manually with a low setpoint (as I mentioned above). The whole point of this exercise is to simulate O2 loss while flying on auto. In that case, the solenoid can no longer maintain a setpoint.

If it is less than 0.7, when is the fail? And who decides that? Just because a reasonable instructor would do it at 0.6 or 0.5, it doesn't mean that some numbnuts instructor won't do it at .18.

So because a theoretical incompetent instructor might do a drill wrong and kill a student, the drill shouldn't be done? A numbnuts instructor might tell a student that they don't need bailout. Does that mean that agencies should prohibit CCR training altogether?

I run a scientific dive program so maybe I tend to think about the liability aspect more than most, but in my mind training should be about minimizing risks, especially pointless ones regardless of how small the risk is.

We should do things safely to avoid injuring or killing students, not because of legal liability. Training should be about training. We differ on whether this particular drill is useful or pointless. That's fine.

Look, the decision to dive a rebreather means that you are taking on a significant risk to your life because you want to do a fun leisure time activity. Most of us aren't military or commercial divers. If we are so risk averse that we say that this training method can't be used because a terrible instructor might just sit there and watch his student die, then we shouldn't be doing CCR training at all.

 

[rjack321]

Fair enough. I can't find any post in this thread where someone suggested that.

This thread is in "accidents and incidents" where a young man died close to or at the surface. Hypoxia being a leading contender in the 'why' category.

 

[doctormike]

This thread is in "accidents and incidents" where a young man died close to or at the surface. Hypoxia being a leading contender in the 'why' category.

Oh, so you think that the instructor might have turned off his O2 before he splashed as a test? Yes, I agree, that would be a bad idea. But I don't think that anyone was suggesting simulating O2 feed loss at the surface in the part of the thread where we were discussing that specific drill at depth.