Fatality at WKP

[Jax]

Okay, first let's consider a single mix scenario. If all the bottles you're carrying have the same mix in them, then there's no need to do an MOD check during a switch, 'cause you're just switching bottles, not gasses.
Now let's consider a simpler plan than was likely the case here, but will illustrate the point well. You enter the water at Jackson Blue (max depth about 95' for this dive) with EAN32 on your back. You have a deco bottle of EAN50 and two stages of EAN32 slung. You're breathing your first stage to start the dive, and drop your deco bottle at 70'. Now you have the stage (EAN32) you're breathing, another stage of EAN32, and the EAN32 back gas. So now you're back in the one gas scenario... There's no need to check gasses when you reach switch pressure on the first stage... you just drop it and switch to your second stage, 'cause all the gas you have is the same gas; there's no chance of making a mistake w/r/t MOD, if you made a proper drop at 70'.
So, if all the gas you have is the same gas, then no, there's no need to do any kind of double checking. My point in my previous post is that this mishap tells me that the deco bottle drop must be treated with the same checks as a gas switch when you're carrying different gasses at the drop, because if you screw it up then the "it's all the same gas" procedure will be invalid later in the dive.
Rick

I understand what you are saying, but . . . if you are changing bottles, check the gas. That was drilled in pretty well. If you are picking up a different bottle, you are changing gas. There is no same gas. I'm thinking that firm requirement has a good reason.

 

[Rick Murchison]

I understand what you are saying, but . . . if you are changing bottles, check the gas. That was drilled in pretty well. If you are picking up a different bottle, you are changing gas. There is no same gas. I'm thinking that firm requirement has a good reason.

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

 

[LiteHedded]

the take away from this is that it can happen to anyone. if it can happen to that man it can happen to anyone

 

[Rick Murchison]

Not only do bottle drops need to be treated with the same checks as gas switches, but if you are picking up a bottle someone else dropped, the markings on that bottle need to be checked. Just speculation, but there may have been a little too much trust in the procedures and not enough verification.

I'm not following you here Rob. Are you saying the deep bottle at 70' was perhaps dropped by someone else? Or that the bottle with 70' gas was dropped deep earlier and picked up by the mishap diver?

 

[Rick Murchison]

the take away from this is that it can happen to anyone. if it can happen to that man it can happen to anyone

The whole reason we analyze mishaps is to discover how it happened to anyone and how to prevent it from happening to anyone else. If the using of the wrong gas was because an in-place procedure or protocol was not followed, then no one else need suffer "it" - at least not this "it" - if we, as a community and as individuals insist on absolute obedience to the procedure and protocol.
If there was a defect in a procedure or protocol that allowed this to slip by, then we need to modify one or both to avoid a repeat. Either way, we avoid "it" in the future.
In my case I've identified a weakness in my own procedures and have patched them to prevent this particular "it" from biting me or any of my team.
If, on the other hand, you mean "there's always some other "it" out there than can bite any of us," I agree.
Rick

 

[Indian Valley Scuba]

Help me here....if it is your mouth taking the regulator, who is responsible for verifying the gas? Your team? I think not. Diver - save yourself!

 

[Dive-aholic]

I'm not following you here Rob. Are you saying the deep bottle at 70' was perhaps dropped by someone else? Or that the bottle with 70' gas was dropped deep earlier and picked up by the mishap diver?

The original report I read stated in addition to the 3 team members, there were at least 2 support divers in the water before the convulsions began. I got the impression a support diver dropped the deep bottle at 70'. The 70' bottle, which should have been at 70' was not there, but rather clipped to Jim. To me that implies there was an error in the procedure by more than one person.

 

[TSandM]

I would be surprised if the support divers took the deco bottles down to drop them. Maybe they do, but I think they come to pick them UP at the end of the dive, but the diver takes them down with him. I'd be really, really uneasy, myself, trusting that a team behind me was putting the gas I needed for safety in place. What if someone had ear problems or for some other reason couldn't complete the dive?

Rick, I think your takeaway is an excellent one. 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. So, in that case, the deco bottle drop DOES need to be confirmed. I was not taught that, and it's a good addition to procedures.

 

[Blackwood]

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. So, in that case, the deco bottle drop DOES need to be confirmed. I was not taught that, and it's a good addition to procedures.

Hindsight being 20/20, that seems like a huge oversight to the point that I'm surprised this hasn't happened before.

Full disclosure, I'm not cave trained, and the only course in which we dropped bottles, we dropped all of 'em.

 

[Rick Murchison]

Help me here....if it is your mouth taking the regulator, who is responsible for verifying the gas? Your team? I think not. Diver - save yourself!

Procedure for gas switch:
Pre dive check of bottle contents and labeling of bottle with MOD. We use 3" numbers on the side of the bottle that's visible during carry so it can be easily read from a distance.
1. check depth, retrieve reg
2. trace reg to bottle
3. verify bottle/MOD
4. buddy verifies depth against MOD & that reg is attached to correct bottle & gives ok
5. ensure gas on/check pressure
Now you can complete the switch by breathing off that reg.
Rick