Fatality at WKP

[EastTNDiver]

You're allowed to use your brain in real tech diving If all your bottles have the same gas in them then they have the same gas in them and there's no need to apply artificial rules to their use. Think of sidemount; think of independent doubles; think of all those folks who carry pony bottles...
Now... in defense of your instructor, if you're doing open water AN/Deco, then you're not going to be in a "same gasses all 'round" scenario, are you, 'cause you won't be dropping off your deco bottle on the way down. So every switch you make is a potential gas switch, and every switch must be treated as a possible switch to the wrong gas - and your instructor is absolutely correct.

Rick

With side mount, independent doubles, ponies, you enter the water with all the same gas...typically. My take on this subject is, if you enter the water with even one bottle of gas that varies from the rest, then you are not in a same-gas scenario...even if you drop that bottle. It's all well and good to stress the importance of a correct drop protocol, but doing a verification on the switch would be a redundancy for the drop protocol would it not? We preach equipment redundancy til we're blue in the face, but protocol redundancy is a waste of time?

 

[Jax]

With side mount, independent doubles, ponies, you enter the water with all the same gas...typically. My take on this subject is, if you enter the water with even one bottle of gas that varies from the rest, then you are not in a same-gas scenario...even if you drop that bottle. It's all well and good to stress the importance of a correct drop protocol, but doing a verification on the switch would be a redundancy for the drop protocol would it not? We preach equipment redundancy til we're blue in the face, but protocol redundancy is a waste of time?

Newb & non-cave-diver question again . . . If I do have sidemounts and a stage, and I drop that stage . . . Don't you still check it when you pick it up? Doo-doo occurs, and making assumptions that it is your bottle and gas just seems the height of complacency.

 

[EastTNDiver]

Newb & non-cave-diver question again . . . If I do have sidemounts and a stage, and I drop that stage . . . Don't you still check it when you pick it up? Doo-doo occurs, and making assumptions that it is your bottle and gas just seems the height of complacency.

I would check everything I intend to breathe...pre-dive...at drop...at switch. Complacency is protocol's nemesis.

 

[TSandM]

I was thinking about the "verify deco bottle drop" idea this morning, and it still doesn't cover the problem. As long as you are on a site where there are similar sized bottles filled with gas you can't breathe at depth, I think you HAVE to verify bottle switches. Just because you correctly dropped an 80 of 50% at 70 feet, doesn't mean you aren't carrying another one.

I'll buy that, when your only deco bottles are 40's, it's obvious enough which is which that you aren't going to breath deco gas at depth. But with 80's, you lose that comfort.

Bottom line is, I think, that stage swaps need to be treated like gas switches. I think Jim's death tells us that.

 

[Dan Gibson]

"I was taught in C2 that switches on and off bottom stages did not have to be watched, because after all, it was all the same gas."

I had the same instructor, and that definitely was not the case back in 2003. We watched all switches as a team.

 

[gkndivebum]

[...] Also continues to point to the lack of an O2 sensor on the RB80 as a serious problem (for either hyper or hypoxia, both have happened several times in the recent past)

This bears repeating. One of the things I drill into my rebreather student's heads is "Actively know thy PO2".

Having a means to monitor the PO2 in the breathing loop might have helped prevent this tragedy.

 

[Blackwood]

I was thinking about the "verify deco bottle drop" idea this morning, and it still doesn't cover the problem. As long as you are on a site where there are similar sized bottles filled with gas you can't breathe at depth, I think you HAVE to verify bottle switches. .

Most certainly. Know what you stick in your mouth.

Casey's post seems to indicate that switch verification is per procedure.

 

[DwayneJ]

Also continues to point to the lack of an O2 sensor on the RB80 as a serious problem (for either hyper or hypoxia, both have happened several times in the recent past)

Any other rebreather (with redundant O2 sensors and PPO2 displays), a bottle mixup would have shown up quickly. You have to know your PPO2.

 

[rjack321]

"I was taught in C2 that switches on and off bottom stages did not have to be watched, because after all, it was all the same gas."

I had the same instructor, and that definitely was not the case back in 2003. We watched all switches as a team.

We watched switches as a team. Not so much for the MOD (although we did look) but because regs get junk in them, people cough at exactly the wrong moment, free flows happen... Basically if something can go wrong it will go wrong at a switch.

 

[rjack321]

This bears repeating. One of the things I drill into my rebreather student's heads is "Actively know thy PO2".

Having a means to monitor the PO2 in the breathing loop might have helped prevent this tragedy.

Any other rebreather (with redundant O2 sensors and PPO2 displays) and a bottle mixup would have shown up quickly. You have to know your PPO2.

With the RB80 you are supposed to know the drive gas is correct and your personal ppO2 drop to avoid relying on electronics. Flashing bells and whistles are conciously avoided on the Rb80. I think the current 6/11 issue of Alert Diver has an article on CCR warning gizmos which describes how they are no solution either.