diver death results

decoweenie

This is similar to:

• get into a car sitting on the hill
• do not put the key in the ignition
• pop out of neutral and start "driving" downhill
• blame the car manufacturer for not installing a "rolling switch" to unlock the steering wheel and start the engine when ran off the curve.

People who forget to turn the unit are most likely to dive without turning the tanks on, and other simple and elementary procedures - all of which were drilled and drilled into their heads during the mod-1 course.

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

AD_ward9

Without witnesses or a dive buddy, or access to the dive computer log, then it is impossible for anyone to tell when the unit was turned off. The "Always Know Your PPO2" thread shows plots and explains the differences between:
1. Not turning the unit on before the dive.
2. Bounce shortly after entering the water.
3. Bounce during the dive.
4. If it was turned off during the dive for some other reason at a point other than where battery bounce can occur.

If the profile is available, then entering the profile into the Rebreather verification tool will determine which of the above could have occurred, and which could not. Without the profile, the cause cannot be established. The examiner would also need to use a microscope on the contacts to determine if bounce occurred - probably that was not done.

If the unit was pre-breathed, the chance of (1) above is slight, so the diver should not be slagged off on this forum for that unless someone on this list has the profile.

The problem is if bounce occurs underwater, the diver will try and turn the unit on and off, but due to some software errors, will not proceed with the dive. The result is the unit more often than not is off when the diver is recovered when any of the above faults occur.

Finally, not turning the unit on is totally different to not turning a car on. Rebreathers must turn on automatically if they are to comply with EN61508, which as the unit carries a CE mark, is what it claims to do. There is no way they can meet the SIL 4 requirement in the standards otherwise.

Alex

DepthCharge

I like your thinking on this............makes the most sense.

__________________
Later,
John

It's better to beg forgiveness than ask permission

Genesis

I've done a LOT of thinking about the wet switch issue and I totally disagree with the idea that they're good.

In fact, I'd say they're REALLY BAD.

The possibility of flattening a battery to the point where you have a problem underwater without realizing it is higher than that of going in with the unit off and not looking at the handset prior to the loop going hypoxic and killing you.

BOTH require inattention.

But so does going in with the gas off on OC, and yet according to the DAN statistics this gets, on average, one person a year.

But there is no requirement in CE this-or-that mandating automatic gas valves! They could - but they don't.

So why is it a "good idea" here? Truth - its not. Any more than it is on the tank.

IF the unit faulted due to a bounce and was found off (but was on when it went in the water) that is a serious matter. But - we'll never know, will we? That's what we get for allowing the companies that build these things, or anyone connected to or with them, such as an instructor on that unit, to examine them post-incident.

I've had a dive computer battery flattened due to wet switches (Suunto) in a gear bag. That was a PITA but not particularly dangerous. It really isn't on a CCR either, so long as you look at the display! If you go in the water without looking at the handset, how is this the machine's fault - or responsibility?

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

AD_ward9

The CE issue first: if the unit has any electronics in it, or electrical, then EN14143:2003 requires compliance with EN61508, and that requires SIL4, which means that collectively all the critical failure modes together must have with an incidence of less than 1 per billion hours. As there are only about 5000 rebreathers in active use by sports divers, then if there is one death per year from this cause alone, then the system does meet any Safety Integrity Level required by Table 3 of EN61508-Part 2, and 10,000 times worse than the SIL-4 level required.

On the battery issue, you are absolutely correct. Dead battery should not mean dead diver.

Alex

6Gill

For me, I prefer the discipline that MCCR enforces. My logic was a couple of years on MCCR to establish good habits before going to ECCR. Folks have made some pretty amazing dives on the KISS... way beyond Jetsams spec.

Most of us that dive MCCR prefer to dive the unit rather than have the unit dive us, it still requires the same amount of thought and planning (or should).

I've had the pleasure of diving with very experienced divers who dive both MCCR and ECCR and they frankly admit that they tend to be a little more complacent on ECCR when they are busy, photography etc. To and extent it's human nature.

__________________
"It's a shame ignorance isn't painful!"

kiam

I agree with Schford's statement. The onus for using adhering to a safe Rebreather dive, lies with the diver. I dive a SK and one of the things that attracted me to MCCR vs. ECCR is the responsibility factor of not having a safety net supplied by electronics and the simplicity of an MCCR unit. I am sorrowful any time I hear of a diver dying while using a rebreather, yet pull up short of saying this or that could have been prevented, if this or that safety feature where made available. When we all made a decision to be RB divers, we knew that diligence is the order of the day, we accept that a lack of diligence means there is the possibility of a negative life experience in our future. Wet switches, no wet switches, buzzers, bells or anything of the like can be circumvented, nothing on these units is failure proof; including the diver using the unit. We as RB divers need to man up and accept the responsibility of doing the thing the way it was meant to be done. Stop trying to push our failures off on RB manufactures. My condolences to the divers family.

fireman

One must always behave with respect to the dead, and to dependents when someone dies suddenly. I'm sorry for your loss.
That said, I think the lesson here is complacency--I can grab a tank turn on put a little air in the bc and stick the reg in my mouth and jump in and be almost certain that I will survive. To try that with any rebreather...
I can't help thinking that this is more likely to happen the more automated the system.

I had the germ of a thought the other day: I was talking on my cell phone, and I lost the call, tried again and the battery went dead. Compare the cost and level of complexity of a cell phone to an eCCR. Yes I know there are numerous flaws in the analysis--for example the cell phone is not engineered to be a piece of 5 sigma life support equipement, but it is a multi Billion dollar market that has been optimized by a lot of talented people, and it still screws up. Now one could come back with "the space program argument", but I don't have that much money to spend. I don't even have the money to buy something like a Mk 15x.
My conclusion with admittedly no direct experience--I just bought a orca which will be turned into a mCCR. If I could I would probably get a MK15--But the level of training and "carefulness" required in maintenance and predive procedures might outweigh the robustness of the system when diving.
Which brings up another point: To a certain extent risk sports in general and rebreather diving in particular require you to know yourself. Are you are a panic prone dumb ass or a cool under fire rocket scientist. Are you the sort of person who can do the maintenance to letter of the law every time or somebody who just "dives in". Self analysis is hard but your life hangs in the truth.

Genesis

There are a lot of dumb regulations Alex.

I know you keep banging on this, but there is IMHO a huge difference between a unit that has a battery that bounces and leaves the unit OFF (a serious fault) and one that has a SWITCH that can be TURNED OFF (which technically doesn't meet SIL4 yet IMHO is safer than one that has wet switches!)

Dead power in an ECCR is a serious matter. Even in an mCCR its serious if your PO2 monitoring no longer works.

Attempting to protect people against their own complacency isn't IMHO all that productive. We'd do better if we focused on identifying "surprises" in the way things work (defined: "surprise" = "not documented oh $hits that can kill you.")

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

AD_ward9

On dumb regulations, I do not think a regulation requiring manufacturers to meet 1 billion hour between failure for life critical equipment is dumb at all. Unfortunately a lot of dumb manufacturers have not got the message yet ;-)

Your point 1: IMHO, when there is no power the equipment should have a mechanism which prevents someone breathing from it. Auto Shutoff Valve. Incidentally when an accident is caused by battery bounce the unit sometimes looks off when it happens, even though it is not, but the diver then turns the power switch off and on to try and get it past the software, without success.

Your point 2: Finding new "surprises" would be much more productive use of this column. Without a truly comprehensive list of surprises, designers cannot check their designs respond properly to each of them.

Alex