Is it OK to turn off O2 in Rebreather Training?

[Superlyte27]

1) Instructor and student are swimming at depth, student is on an eCCR at high setpoint (say 1.3).
2) Instructor shuts off O2
3) Student's PO2 slowly drops over several minuts
4) If student notices the drop, they address it (try MAV, check tank valve, bailout if unfixable)
5) If they don't notice it for several minutes and the PO2 drops to, say 0.7, the instructor calmly turns on the O2, and the only way the student realizes what happened is they get a "you fail" flash card

I think you guys are also forgetting: as soon as ppo2 hits 1.2, the solenoid continues to fire over and over and over again trying to resolve the deficit. This is an apparent, loud and empty click. On the Optima and Liberty, it'll probably fire 30 times in a minute. If you can't catch that before you drop to a 1.1ppo2, I show you a card that reads, Your Oxygen Is Off".

Seriously, 30 clicks in a minute, instead of a few shots of oxygen every minute, and you don't have the where with all to notice. You're not getting a card this day.

 

[boulderjohn]

But that's the same for any training risk, right? It's possible for all sorts of things to go pear shaped - loop recovery, open water lost regulator drill, CESA, lost line drills, etc... All of these things have caused accidents.

If an incident occurs while you are doing an agency sanctioned exercise according to standard protocols, in a trial, the burden would be on the plaintiff to prove that the standard approved protocols are not only unsafe, they are so very unsafe that you should have realized it and gone against standard practice. That will be almost impossible.

If an incident occurs while you are doing something that is not sanctioned by the agency and not a standard protocol, the burden would be on you to prove that what you were doing was safe. Your burden would be ever more difficult because of the fact that your agency does not approve of it, implying the agency does not believe it is safe. Furthermore, your agency may well testify that it believes the procedure was unsafe, and that is why they expelled you when they found out what you did. (And, yes, that has happened.)

 

[Superlyte27]

If an incident occurs while you are doing an agency sanctioned exercise according to standard protocols, in a trial, the burden would be on the plaintiff to prove that the standard approved protocols are not only unsafe, they are so very unsafe that you should have realized it and gone against standard practice. That will be almost impossible.

If an incident occurs while you are doing something that is not sanctioned by the agency and not a standard protocol, the burden would be on you to prove that what you were doing was safe. Your burden would be ever more difficult because of the fact that your agency does not approve of it, implying the agency does not believe it is safe. Furthermore, your agency may well testify that it believes the procedure was unsafe, and that is why they expelled you when they found out what you did. (And, yes, that has happened.)

Good thing this topic isn't about an issue that is actually against standards then.

 

[doctormike]

If an incident occurs while you are doing an agency sanctioned exercise according to standard protocols, in a trial, the burden would be on the plaintiff to prove that the standard approved protocols are not only unsafe, they are so very unsafe that you should have realized it and gone against standard practice. That will be almost impossible.

If an incident occurs while you are doing something that is not sanctioned by the agency and not a standard protocol, the burden would be on you to prove that what you were doing was safe. Your burden would be ever more difficult because of the fact that your agency does not approve of it, implying the agency does not believe it is safe. Furthermore, your agency may well testify that it believes the procedure was unsafe, and that is why they expelled you when they found out what you did. (And, yes, that has happened.)

Yup. I'm not an attorney, but that sounds right. So I guess the question is - is the O2 shutoff against standards? At least one post upthread says it isn't, for some agencies.

 

[KenGordon]

I am against having o2 turned off, however I did have a very illuminating experience when I turned it off for a boom drill and failed to turn it back on.

I had been diving CCR for a year and had maybe 50 hours. I joined the last couple of days of a MOD1 course so as to get a critique from my instructor and told off for anything I had forgotten or was doing wrong.

Following a burst hose drill I failed to turn my O2 back on. Some time later I was given a low ppO2 card and I was quite surprised to see I really did have low ppO2. I was convinced, although very surprised, in the water that the instructor had turned off my O2 and it wasn’t until we surfaced that I learned the full extent of my incompetence.

This was an extremely sobering event and probably my most memorable piece of learning on CCR (up there with nobody is going to manage a CBL so make sure you never need one).

Seeing as it is a known flaw I make a very concious effort to check my ppO2 enough, however I have not had a failure to detect so that effort is untested.

BTW I think some posters in this thread ought to do some maths about how much o2 is in the loop at a given setpoint at different depths. Fractional pressure vs partial pressure and all that.

 

[njdiverjoe]

I am against having o2 turned off, however I did have a very illuminating experience when I turned it off for a boom drill and failed to turn it back on.

I had been diving CCR for a year and had maybe 50 hours. I joined the last couple of days of a MOD1 course so as to get a critique from my instructor and told off for anything I had forgotten or was doing wrong.

Following a burst hose drill I failed to turn my O2 back on. Some time later I was given a low ppO2 card and I was quite surprised to see I really did have low ppO2. I was convinced, although very surprised, in the water that the instructor had turned off my O2 and it wasn’t until we surfaced that I learned the full extent of my incompetence.

This was an extremely sobering event and probably my most memorable piece of learning on CCR (up there with nobody is going to manage a CBL so make sure you never need one).

Seeing as it is a known flaw I make a very concious effort to check my ppO2 enough, however I have not had a failure to detect so that effort is untested.

BTW I think some posters in this thread ought to do some maths about how much o2 is in the loop at a given setpoint at different depths. Fractional pressure vs partial pressure and all that.

I have a similar story -- during my CCR training we were manually maintaining a high setpoint with the controller as a parachute on the low setpoint. After a boom drill I forgot to turn my O2 back on -- on my next ppO2 check I saw that it was low and hit the MAV and got nothing. I turned O2 back on, looked up and of course my instructor is watching me like a hawk asking me if it's on now.

Of course this is something different, and isn't exactly the same thing as the instructor turning off your O2. However, I want to point specifically that the unexpectedness of hitting the MAV and not getting anything made it a really memorable learning moment. You can be sure I never made that mistake again.

 

[doctormike]

Following a burst hose drill I failed to turn my O2 back on. Some time later I was given a low ppO2 card and I was quite surprised to see I really did have low ppO2. I was convinced, although very surprised, in the water that the instructor had turned off my O2 and it wasn’t until we surfaced that I learned the full extent of my incompetence.

That seems to be an example of how the sneak-shutoff drill would have been very helpful for you at that point. I mean, if you needed an instructor with a card to remind you to always know your PO2, and you were surprised by suddenly seeing a low reading, that's definitely something that could be addressed by this sort of training. I'll be you were a lot more situationally aware with regard to monitoring your PO2 after that, right?

Not criticizing you particularly, I have done the same thing. I'm just saying that it's something helpful for an instructor to address. So when people say this drill is worthless, this would be one reason why it isn't.

 

[doctormike]

I have a similar story -- during my CCR training we were manually maintaining a high setpoint with the controller as a parachute on the low setpoint. After a boom drill I forgot to turn my O2 back on -- on my next ppO2 check I saw that it was low and hit the MAV and got nothing. I turned O2 back on, looked up and of course my instructor is watching me like a hawk asking me if it's on now.

Of course this is something different, and isn't exactly the same thing as the instructor turning off your O2. However, I want to point specifically that the unexpectedness of hitting the MAV and not getting anything made it a really memorable learning moment. You can be sure I never made that mistake again.

Right, and we accept the fact that in a boom drill, the instructor is responsible for making sure that the student turns the O2 back on. Why can't the instructor take on that same responsibility for the sneak-shutoff drill?

 

[Superlyte27]

Right, and we accept the fact that in a boom drill, the instructor is responsible for making sure that the student turns the O2 back on. Why can't the instructor take on that same responsibility for the sneak-shutoff drill?

I have to wonder if the instructor missed that it didn't get it turned back on, or was waiting to see how the diver handled it possibly 10 minutes later. I personally check the o2 bottle every single time after a boom drill. I don't want any surprises or compounded issues later when perhaps something else might be going on.

 

[njdiverjoe]

I have to wonder if the instructor missed that it didn't get it turned back on, or was waiting to see how the diver handled it possibly 10 minutes later. I personally check the o2 bottle every single time after a boom drill. I don't want any surprises or compounded issues later when perhaps something else might be going on.

I don't remember all the details but we were shallow and the whole thing happened within a minute or two -- when the boom drill was sprung I was probably really close to needing to add O2, it probably went something like...

1) boom drill
2) forget to turn O2 on
3) check pO2, breathable but will need to add momentarily
4) kick up or down to stop from bouncing off the platform or float away (I'm sure everyone remembers those first couple ccr training dives and what happens when task-loaded)
5) check pO2, time to add, hit MAV ...
6) Ah! Turn O2 back on