Error Blue hole fatality

[justinthedeeps]

Indeed let's try to understand how it came to be that a[nother] presumably well trained diver ended up breathing a deco gas at depth, and what might have been the opportunities to catch or avoid that in this case.

Enough of the "just switch properly" talk (we all know that, mates.....)

 

[Learner Diver]

I have two questions:

1. What are the standards for verifying an instructor's gas switch in tech training?
2. What bottle would he be switching to at depth and why?

Regarding #2 - if he had a bottom stage, wouldn't it be normal procedure to breathe that first and then switch to back gas when the stage is almost empty? It seems unlikely that he would mistake the stage for his back gas if the stage reg was stowed?

Good question. I been told by some technical divers who prefer to separate cylinders from left to right, and have the cylinders marked with the gas percentage and depth, in which it can be breathed.

 

[steinbil]

But it can happen. The WKPP had this very mistake on a dive, and the WKPP is famous for its insistence on proper gas switching technique. A diver in a group left his stage bottle on the depot for 50% bottles and took his 50% bottle to 200 feet.

I don't know the details of this accident (was there a report?) or the procedures for dropping stages in caves, but isn't it more likely to be a lapse in gas verification procedures (complacency?) than for two divers to mistakenly identify the MOD of a bottle at the same time? I might be wrong, of course, but I can see how easy it would be to start getting sloppy with these procedures after hundreds or thousands of gas switches.

We don't have any details on what happened, so let's not go too far on assumptions. When I have read reports on fatalities (and near fatalities) over the years, it seems to me that in the majority of the cases, the switch itself was fine. The problem was that what was in the tank was not what the diver believed it to be. The real error happened on the shore before the dive.

Good point. I didn't mean to imply that the switch was the cause, I just read the article to mean there was a switch, but I might have misinterpreted that, and it made me wonder about standards for instructor's gas switch since it happened to an instructor on a tech class dive. I can see how failure to analyze gas might be even more likely.

 

[boulderjohn]

I don't know the details of this accident (was there a report?) or the procedures for dropping stages in caves, but isn't it more likely to be a lapse in gas verification procedures (complacency?) than for two divers to mistakenly identify the MOD of a bottle at the same time? I might be wrong, of course, but I can see how easy it would be to start getting sloppy with these procedures after hundreds or thousands of gas switches.

I am talking about a failure to properly identify the contents of a tank on the surface. You may think your tank has a certain mix and properly mark the MOD, but it turns out to be something other than you thought it was. The diver may remember that the tank had a certain fill, or there may be an old marking on it that was not verified.

 

[steinbil]

I am talking about a failure to properly identify the contents of a tank on the surface. You may think your tank has a certain mix and properly mark the MOD, but it turns out to be something other than you thought it was. The diver may remember that the tank had a certain fill, or there may be an old marking on it that was not verified.

So in that case a failure to analyze the gas.

 

[boulderjohn]

So in that case a failure to analyze the gas.

Correct. That has been the problem in the majority of cases I have read about over the years.

 

[justinthedeeps]

Could easily mix up cylinders during in-water sidemount prep, or any time when clipping on mixed-purpose stage cylinders.

Someone simply hands you cylinders in a reverse order during a busy entry....
Then just assume "this is my normal config now."

So there's the weakness of "your gases will always be in this one single config" approach. You will never expect it to be different, and thus may stop actually verifying anything.

People think solo diving is bad... being an instructor is far more dangerous. So many distractions.

How many times have you & your buddy (or your instructor) actually tried to catch each other out, by pretending to offer the wrong gas, or switch to the wrong gas on purpose? Mix up the cylinder order and positioning? I am guessing zero, for most of us.

 

[justinthedeeps]

Here's another one that could rile some of the "there is only one good way=my way" folks:

During setup and pre-descent checks, you can pressurize your deco stages, test them, and then re-close the valves to "just a crack open" (to prevent first stage flooding). You will need to reopen these valves to breathe from them. Which you will have plenty of time to do when you reach your deco stops. Below that depth, you can neither tox out on them, nor lose the gas, without spending the time to re-open the valves.

 

[Nick_Radov]

Good question. I been told by some technical divers who prefer to separate cylinders from left to right, and have the cylinders marked with the gas percentage and depth, in which it can be breathed.

No diver with any common sense or proper training would ever rely on stage tank location or separation to distinguish between mixes. I have heard of divers coming up with convoluted "solutions" like putting the lower oxygen mix on the left and the higher oxygen mix on the right (sometimes with additional nonsense like color coding or regulator covers or whatever) but this gets in the way of other gear like the long hose and light cord in a typical backmount doubles configuration. Plus something like a sixth of the population suffer from left-right confusion. And schemes like this totally fall apart once you progress to more complex dives with 3+ stages.

Only rely on proper cylinder markings.

 

[justinthedeeps]

No diver with any common sense or proper training would ever rely on stage tank location or separation to distinguish between mixes. I have heard of divers coming up with convoluted "solutions" like putting the lower oxygen mix on the left and the higher oxygen mix on the right (sometimes with additional nonsense like color coding or regulator covers or whatever) but this gets in the way of other gear like the long hose and light cord in a typical backmount doubles configuration. Plus something like a sixth of the population suffer from left-right confusion. And schemes like this totally fall apart once you progress to more complex dives with 3+ stages.

Only rely on proper cylinder markings.

This is certainly correct, but is it sufficient for all situations? What is the protocol for complete loss of light in a wreck or cave? Or both masks gone?