Fatality at Jersey Island

[gianaameri]

Is there any evidence that the unit was "incorrectly assembled" other than the coroner's report? Details on what exactly "incorrectly assembled" means? Any training or credentials cited that would allow the coroner to make that call? I'm willing to believe she died due to a CO2 hit, but beyond that, I'd want to hear more before I toss my Prism 2 in the dumpster.

Yes, but I am sure Hollis being a reputable and good company will address any issues free of charge, if they have not already done so.

So, no need to bin anything, but be careful if yours can be incorrectly assembled as this is the lesson to be learned (maybe contact Hollis for advice).

 

[Dr. Lecter]

This one lady that died in this incident was a diving instructor.

If she can't assemble the rebreather correctly, who can?

Unless she's a rebreather instructor, she may as well be a knitting instructor. But your point isn't wrong: even CCR instructors are not magically immune to human error, and the answer to your question is that statistically speaking nobody will assemble a rebreather correctly 100% of the time.

Which is why we have and use build lists, closed checks, prejump checks, and in the water practices like bubble checks/6m O2 flushes/the occasional dil flush...all of which, when combined with a functioning human brain, let you figure out for yourself if the unit is working correctly. There are still things - like CO2 buildup, as apparently happened here - that we can't really check for. If you screw up a build in a way that creates that kind of fault, then there's an excellent chance you're going to die.

Which is why you think BOVs are some kind of obvious, 'should be mandatory' solution. And that's fine, so long as you confine the reach of your conclusion about whether the BOV's extra protection is worth its extra complications and risks to your own damn diving. The rest of us have a different conclusion about whether design elements like a BOV are useful enough to merit inclusion.

As in all things, designing CCRs to negate all consequences of human stupidity is neither possible nor desirable. It's impossible because fools (and we all are, from time to time) are so ingenious. It's undesirable because while you'll save the occasional fool, the additional complexity will eventually lead to other fatal failures and the rest of us will have to deal with a machine designed for the lowest common denominator. And since we tend not to be an accepting, compliant lot, we'll instead mod units or go full home-brew. Having marketplace sufficiently lightly regulated that it allows for a wide variety of safety and design philosophies to compete is bound to work out better in the long run.

Which is not to say I don't appreciate and encourage simple, elegant design choices that reduce or eliminate risks of human error going undetected: I do, and like Potter Stewart, I know the right balance when I see it. I just don't get the 'everything I think is good should be mandatory, and everything I think is bad should be prohibited' philosophy.

 

[TSandM]

Bear with me -- the first part of this post will seem irrelevant.

Many years ago, we lost a foal who was born prematurely. He went to the vet hospital, where they put him on oxygen, by putting a red rubber tube down his nose, and attaching some IV tubing to it. He also had an IV. After some hours, when he got strong enough to try to get up, they would disconnect both sets of tubing, let him try (they flail a lot in the process, which is why they disconnected everything), and then hook everything back up when he gave up and laid down. At 4am, they hooked the oxygen to the intravenous catheter and put 15 liter of gas into his bloodstream, and killed him.

One of our requests to the vet hospital was that they change their procedures so that this simply couldn't be possible (different tubing). Our Children's Hospital in Seattle did the same thing, when a neonates's tube feedings got hooked to an IV catheter and killed the baby.

Human error is not avoidable. It seems reasonable that, to the extent possible, things which are mission-critical ought to be designed so that improper assembly is not possible. It's not that hard to do -- just using incompatible fittings will prevent a lot of misassembly. Now, if this was a scrubber packing issue, that may be unavoidable. And if something was put together without an o-ring, or with a pinched o-ring, that may not be preventable, which is where pre-dive checklists come in.

 

[rongoodman]

The Prism 2 does have incompatible fittings, so that the loop can't be attached backwards.

 

[gianaameri]

The Prism 2 does have incompatible fittings, so that the loop can't be attached backwards.

Is that still the case if you reverse the left and right counterlungs and/or the one-way valves?

Any other ways it could be done in error?

 

[gianaameri]

Here is one: One of our divers encountered a Prism diver who thought that by filling up his scrubber half way is helping him to conserve sorb! Wonder who trained him! So if this guy had died, it was not because of manufacturing error, but because of poor training. Just like "baking" sorb or disturbing the sorb bed otherwise.

I don't think that even the Apoc would be able to remedy this.

I had been wondering why manufacturers introduced pre-packed disposable scrubbers (be that with granular absorbent or EAC).

Maybe they did to meet this requirement (“It shall not be possible to assemble or combine the components or parts in such a way that it can affect the safe operation and safe use of the apparatus, e.g. by incorrect connection of the hoses to the breathing circuit.&#8221.

You must not forget the target market of the "PADI Type rebreathers" (they are for the ordinary divers, normal ordinary people who make ordinary mistakes if you give them the opportunity to, not necessarily people as good as you).

---------- Post added November 27th, 2014 at 05:29 PM ----------

Somebody else has published on the internet some more information, so here I repeat what they published:

The main findings of the inspection of the equipment were: The rebreather did not comply with clause 5.1 of BS EN 14143: 2013 or BS EN 14143: 2003, which states:
“It shall not be possible to assemble or combine the components or parts in such a way that it can affect the safe operation and safe use of the apparatus, e.g. by incorrect connection of the hoses to the breathing circuit.”
1) The rebreather had been put together such that the gas would not circulate in the required loop and CO2 would not be removed from the inhaled gas.
2) The inhale counter lung was positioned to the diver’s right hand side, instead of the left hand side.
3) The exhale counter lung was positioned to the diver’s left hand side, instead of the right hand side.
4) The one way inhale valve that should be positioned on the inhale side of the mouthpiece, to ensure the gas circulated the loop, was found butted against the one way exhale valve of the mouthpiece stopping any gas passing into the exhale counter lung on the diver’s right hand side.

There is 7 more bits of information which I have, but which yet remains unpublished on the internet.

 

[tstormdiver]

Is there any evidence that the unit was "incorrectly assembled" other than the coroner's report? Details on what exactly "incorrectly assembled" means? Any training or credentials cited that would allow the coroner to make that call? I'm willing to believe she died due to a CO2 hit, but beyond that, I'd want to hear more before I toss my Prism 2 in the dumpster.

The Prism2 will not work in the pre- dive checks if the loop is incorrectly assembled. This can be found by properly following the assembly & pre- dive checklists thoroughly. It would place mushroom valve against an opposite mushroom valve. The hoses are also keyed so that if the wrong hose is attached to the wrong counterlung, the loop will not seal, thus the Positive & Negative pressure tests will fail. The only way for Co2 bypass is a damaged or deformed mushroom valve (can be detected by stereo & positive & negative pressure tests on the lower loop), missing, improperly placed or missing CO2 seal &/ or improper or incomplete packing of the sorb.

 

[Dr. Lecter]

2) The inhale counter lung was positioned to the diver’s right hand side, instead of the left hand side.
3) The exhale counter lung was positioned to the diver’s left hand side, instead of the right hand side.
4) The one way inhale valve that should be positioned on the inhale side of the mouthpiece, to ensure the gas circulated the loop, was found butted against the one way exhale valve of the mouthpiece stopping any gas passing into the exhale counter lung on the diver’s right hand side.

I do not dive a P2, though a couple people I know do and I've seen one built several times before. 2 and 3 are bizarre enough - they don't look alike:


But 4) is just too weird for me to wrap my head around. It sounds like a flapper valve was actually out of position inside the BOV/DSV, against the exhale flapper. I'm not familiar enough with the Hollis design to know if simply breathing on it while the loop was reversed could dislodge a flapper, but I suspect not. So either someone tinkered with the assembly and put it back together wrong, or a flapper valve suffered a catastrophic failure and jammed the gas path inside the loop.

Mixing up the CLs makes me think it's the former, but it's possible that it was the latter and that was the true cause of a fatality. If you completely reversed the gas path within an otherwise correctly assembled P2, you'd get suboptimal WOB and maybe some other relatively minor issues, but I don't think you'd necessarily get hypercapnia or an inhale flapper jammed against an exhale flapper. But whether you put it together right or not, having your inhale flapper get sucked out of place and jam against the exhale flapper's spider...yeah, that'll you up good.

 

[Dr. Lecter]

It would place mushroom valve against an opposite mushroom valve.

Can you elaborate on this a bit? My revo uses a basic Draeger DSV (inhale mushroom in a spider on my right, same thing for exhale on my left), and when I mentally flip the DSV I just don't see any problem for the DSV itself. Yes, I'll be pulling gas from the left and pushing it out to the right, and on the revo that's not good for a number of reasons...but it shouldn't hurt the mushrooms themselves. Am I missing something, or is it maybe the Hollis design different?

 

[descent]

How are the counterlungs attached to the harness?

Do they use identical types of Fastex buckles, like smaller versions of the waistband buckle? Those things are interchangeable, and even work inverted.