Fatality at Jersey Island

[KevinNM]

The best place to put a CO2 sensor would, IMHO, after the scrubber on the inhale side. My understanding was the re-breathed air in question was not getting to the inhale side but was moving back-and-forth between the deceased's lungs and the exhale counterlung. It would make no sense, IMHO, to put a CO2 sensor where you KNOW there will/should be CO2 flowing....right?

It depends. The advantage of using a sensor at the mouthpiece is that you can determine that the sensor is working (you should see very low CO2 at inhale and 5-6% at exhale), and might possibly also detect CO2 overload from the divers activity. As a drawback this seems like pretty difficult and hostile place for a sensor like this to live. Does anyone know where the few rebreathers that have CO2 sensors have them positioned?

 

[gianaameri]

You can watch for one yourself at the Hollis website. There is a chronological list of notices.

Recall / Quality Notices | hollis.com (News - Recall / Quality Notices)

It is not that straightforward.

You provided a US link, which is not the UK one here: Hollis: Scuba Diving Equipment .

As previously posted for the purpose of a practical example/explanation, I own (as do many others) two high power rifles in the U.K. with faulty trigger/safety subject of a recall in the U.S., but not subject of a recall or of any safety notice in the U.K.

So, you can have a product Recall or Safety Notice in one country, but not another, and the U.K. Trading Standards system sucks (literally, being decentralised and fragmented and paying lip service to manufacturers) big time (if there is two or more ways to do something wrong, and this can result in a catastrophe, they are perfectly capable of getting it wrong many times, before they get it right, if ever).

Same could apply to Hollis Prism 2, hence hope you won't mind me asking from time to time just to avoid missing something important.

 

[MalibuJerry]

I think the question is really a broader one: Clearly this was a case in which the operator did about as much wrong as could be possible and I don't understand how that could happen, but should Hollis have made a device which could not be assembled in such a way? There are two points of view as I read these threads:
1. Yes equipment not made so that it is fool (dummy) proof in the sense that every conceivable way in which it can be operated incorrectly is covered, or if not, when discovered, recalled and changes to fix the issue.
2. No, companies should not be responsible for operators not reading instructions properly and not following the proper protocol. It is up to the user to choose how to use the equipment as long as the operating manual shows how to use it safely.

The impact of the two on diving (and other things) is if we go with 1. then we increase costs and reduce risk taking by equipment manufacturers. That means that having the equipment we want to do the things we want to do may not happen. If innovation has high costs to the innovator, innovation does not occur. Here we are pointing to one case Hollis Prism 2, but one case sets a precedent for all. Would we even have scuba today if manufacturers of scuba equipment were liable for "design flaws" in the days before spg's for example? To be sure some and perhaps a lot of garage manufacturers would have made equipment for themselves and friends, but I would venture a guess that the sport would be quite different today.

2. Individuals are responsible for themselves. That allows for the development of new, more risky equipment, and its dissemination and use. Can you assemble it backwards? Yes. If you are properly trained and follow the protocol knowing that if you do so you are asking for a world of hurt, no not really.

Between 1 and 2 I will always pick 2. Innovation is risky, exploration is risky, and technical activities require one to be vigilant. I prefer to have the opportunity not taken away just because someone did not have the discipline to put a rebreather together correctly.

 

[gianaameri]

1. Yes equipment not made so that it is fool (dummy) proof in the sense that every conceivable way in which it can be operated incorrectly is covered, or if not, when discovered, recalled and changes to fix the issue.

No, no one expects or demands that.

Only that the risk is reduced to "as much as reasonably practicable."

To make a rebreather - which can kill you without warning and hope for self-rescue - whose parts can be incorrectly connected to each other is equally dumb and foolish than incorrectly connecting them, but this is human nature - we all make stupid mistakes sometimes.

This is because as simple and inexpensive design feature like left-hand and right-hand thread could have prevented this fatality.

 

[victorzamora]

No, no one expects or demands that.

Only that the risk is reduced to "as much as reasonably practicable.".

You seem to expect that level from Hollis. "Reasonably practicable" is a hugely vague statement. This unit is impossible to put together incorrectly and still have it actually pass all tests, correct? Testing is part of the assembly sequence, correct? From my perspective and definition of "reasonably practicable" Hollis went well above and beyond. Could more be done? Probably. Should it? Depends on who you ask. I mean, people WITH the unit didn't think it was possible to assemble it that incorrectly.

As for the CO2 sensor in the mouthpiece, it seems unreasonable to me to expect a CO2 sensor to ignore "normal" high CO2 levels upon exhale but expect "normal" low-but-nonzero levels upon inhale and actually assume it's correct. Plus, a CO2 sensor in the mouthpiece would be a miserable feat of engineering, and you could never change mouthpieces or, depending on the design, the loop hoses. It simply doesn't make sense to me to introduce another breach right there. Plus, the sensor could false-trip upon high exertion levels or incorrectly closing the DSV. It would make MUCH more sense to put the CO2 sensor right next to the rest of the sensors, after the scrubber, right where it's assumed to have an actual zero-reading so that any elevated reading sends alerts. All CO2-monitored 'breathers I've seen (admittedly not the best person to make this statement) have them in the head, a location that the deceased's unit cleverly circumvented.

 

[gianaameri]

You seem to expect that level from Hollis. "Reasonably practicable" is a hugely vague statement. This unit is impossible to put together incorrectly and still have it actually pass all tests, correct? Testing is part of the assembly sequence, correct? From my perspective and definition of "reasonably practicable" Hollis went well above and beyond. Could more be done? Probably. Should it? Depends on who you ask. I mean, people WITH the unit didn't think it was possible to assemble it that incorrectly.

As for the CO2 sensor in the mouthpiece, it seems unreasonable to me to expect a CO2 sensor to ignore "normal" high CO2 levels upon exhale but expect "normal" low-but-nonzero levels upon inhale and actually assume it's correct. Plus, a CO2 sensor in the mouthpiece would be a miserable feat of engineering, and you could never change mouthpieces or, depending on the design, the loop hoses. It simply doesn't make sense to me to introduce another breach right there. Plus, the sensor could false-trip upon high exertion levels or incorrectly closing the DSV. It would make MUCH more sense to put the CO2 sensor right next to the rest of the sensors, after the scrubber, right where it's assumed to have an actual zero-reading so that any elevated reading sends alerts. All CO2-monitored 'breathers I've seen (admittedly not the best person to make this statement) have them in the head, a location that the deceased's unit cleverly circumvented.

Since there is no Safety Notice, I have no expectations. Nothing will happen.

You fail to see that something as simple and cheap as a left-hand and right hand thread to prevent the loop being reversed meets the "reasonably practicable" test and could have prevented this one fatality even without a CO2 sensor.

So, I give you that prescriptive norms may be required to define what amounts to "reasonably practicable."

 

[Dr. Lecter]

Since there is no Safety Notice, I have no expectations. Nothing will happen.

You fail to see that something as simple and cheap as a left-hand and right hand thread to prevent the loop being reversed meets the "reasonably practicable" test and could have prevented this one fatality even without a CO2 sensor.

So, I give you that prescriptive norms may be required to define what amounts to "reasonably practicable."

What makes you think someone as clueless and unthinking as whomever assembled this P2 wouldn't have cross threaded the out of those left/right hand threads?

You're claiming whatever you think you can get away with is "reasonably practicable" - when that fails, I expect you to move the goal posts again.

 

[HIGHwing]

As a pilot, I have read hundreds of aviation accident reports, perhaps a thousand or more. My "favorite" reports include narratives that explain what the pilot(s) were doing the hours before the flight, or even the day(s) before the flight. You'll see common threads of training gaps, and even external stressors that appear to help enable the accident. As is typically cited, the FAA has stated in the past that it appears to require about four wrong decisions serially to achieve an incident/accident.

In the early 1970s Eastern 401 inexplicably crashed in the Florida Everglades in a very gentle and [some say] controlled descent. The L1011 was probably the worlds most advanced wide body aircraft at the time of the accident, the crews were handpicked, presumably the best of the best. The night of the crash, the only mechanical condition the crew had to overcome was a burned out light bulb on the nose gear. Had this air crew simply tested the light (which they did) and trusted the result of burned out light bulb (which they didn't) they would have landed, replaced the $12 bulb and gone home for the holidays. Eastern 401 ultimately revealed everything we were doing in air-crew training was completely and fundamentally wrong. A skim of the accident will tell you the captain's belly bumped the control column, it disconnected the altitude hold, and no one noticed while they tried to remove and replace the light bulb. But ultimately the findings [aided by the CVR] revealed the crew didn't know how to function as a team and everyone stopped flying the airplane almost simultaneously to fix an unnecessary light bulb prior to an otherwise normal landing.

To me, this accident highlights that it’s necessary to look at parallels between various trained humans performing technical but dissimilar tasks. At the risk of being unpopular, there is probably no better, and no worse team than a husband and wife conducting technical dives together. The married couple involved in this accident is representative of two people who are probably so familiar with each other they can likely communicate with facial expressions; but they are also two people who are equally accustomed to the division of tasks.

To my knowledge, not much has been written about the additional complexities of a married couple technical diving, but in my opinion the issue is real and requires some thought. I also foresee similar issues when technical divers in a team are so intimately familiar with one another in the water things can tend to get delegated to trustworthy people well before the dive. You’ll see the guy with the biggest truck making a run by himself to the fill station. Or, the husband sets up the doubles, stages, and/or rebreather for the wife so she can sleep in a bit. Whatever the specific circumstances on a given dive or set of dives the divisions of labor tend to erode some of the tenants of technical diving in a quest for efficiency or convenience.

To properly evaluate this accident and learn the most we can from it, I think we need to know what happened the day before, and the morning of the dive. Who put it together? What was going on during the assembly and testing in the environment that allowed the assembler/user to make such an unlikely mistake? What was the time schedule for this dive? Were the divers on-time for the dive boat? Were checklists present, or were they accidently left behind?

As Victor pointed out, the assembler of this unit made a very unusual error and I believe there is a REASON for the error that is larger than the design of the unit. I’d be very interested to see if there is anything we can learn from the pre-dive variables that contributed to the fatality.

 

[gianaameri]

Or, the husband sets up the doubles, stages, and/or rebreather for the wife so she can sleep in a bit.

It is purely speculation at this stage that the husband had set-up the deceased rebreather.

However, on the theme you introduce again and again:

1. If it were an OC dive with OC equipment of a recreational nature (14 meters...), what is wrong with the husband setting up the equipment for the wife (or a father setting up the equipment for a son)?
2. If it were a rebreather (we know it was a Hollis Prism 2), why should it be any different from a perspective of somebody who is sold a rebreather which is safe, and EN14143, and cannot be misassembled?

My point is, you do have to look at it from the perspective of the newly certified user (the deceased was), including a married couple (they were married), being sold a finished and certified product (not a homebuilt or prototype) in the way which is marketed nowadays (i.e. a "Hollis" product, Hollis being synonymous with quality and integrity and not the garden shed rebreather companies we were accustomed to in the early days).

 

[descent]

... this accident highlights that it’s necessary to look at parallels between various trained humans performing technical but dissimilar tasks. ... As Victor pointed out, the assembler of this unit made a very unusual error and I believe there is a REASON for the error that is larger than the design of the unit. ...

That was a thoughtful and insightful post, and after reading it, I'm glad I took the time to.

The growing science of human factors in the cockpit has provided us with a marked increase in aviation safety. The retail consumer diving industry (non-commercial, non-military) has still got a long ways to go to integrate these new ideas about human reliability when performing complicated tasks in teams.

You and many others have pointed out before that the design should not be expected to catch every bizarre user input. I think this is sensible. (Differences of opinion on this probably belong in the other thread.)

Design quibbles aside, this accident had "incorrect setup" written all over it. The "second person" theory is compelling, and I don't think it has been discussed nearly enough.