Rebreather Discussion from Brockville Incident

[HIGHwing]

I do not buy it one moment that Wes Skiles was unable to dive an Optima rebreather.

Wow. You fail at conclusions.

 

[flots am]

PADI issued C-Cards for the Voyager.

They also issue a "wreck" cert but anybody who does a significant penetration with one has a death-wish.

---------- Post added July 8th, 2013 at 04:23 PM ----------

I really believe there needs to be some other fail safe system for things that can kill you. Alarms, something, when the PO2 is getting too high or two low or you've packed your scrubber improperly. Humans are human and they always will be.

I have a huge number of drysuit dives, but last month forgot to connect the inflator hose to my suit. It was annoying and embarrassing, but not fatal.

This reinforced my belief that I can not do anything perfectly forever, and that at some point, I'll screw up, so the current rebreathers are all on my "Stuff to avoid because I'll probably die" list.

flots.

 

[Chris Brown Tech]

I was a Missile Launch Officer in the Air Force for four years and worked as an Instructor for the last 18 months, prior to going into the the Army. In the Army, I was the Corps Surgeon for 3 Corps Artillery. With both these jobs we did a lot of evaluation and training.
one of the most common reasons for failure in missiles, where a checklist was used for every single tiny little thing, was missing a step. It is incredibly easy to skip a step in a checklist, even critical checklists when two crew people are checking each other. This was the most common reason a crew would be failed in the trainer scenarios. They would skip a critical step in and emergency or launch checklist.
I can see this happening easily with rebreathers, when a diver is working by themselves and not being evaluated once or twice a month in a simulator. Heck, maybe not even diving once or twice a month!

I really believe there needs to be some other fail safe system for things that can kill you. Alarms, something, when the PO2 is getting too high or two low or you've packed your scrubber improperly. Humans are human and they always will be. That's why surgeons, no matter how careful they are will never be completely without human error and pilots will never be perfect. Humans are imperfect and attention to detail is something that all humans will eventually fail, but hopefully not at a critical step while diving a rebreather, flying an airplane or launching a Minuteman 3 missile.

I agree and I mentioned this recently in one of the many recent anti-ccr peppered threads, might even be this one. Your reasons are exactly why less commercial jet pilots crash than light aircraft pilots despite the additional complexity.

However the bit about alarms is not correct. We already have alarms, buzzers, lights etc available for high, low PO2 and thermal profiling / temp stiks to monitor scrubber usage. We are starting to see scrubber indicators to show they are fitted.

 

[Doppler]

Rebreather technology is young and imperfect. OC technology is mature, tried, and tested.

Not really. First Open-circuit scuba is generally accepted to be the AquaLung invented in early 1940s.

First rebreather is generally accepted to date from the patent for Henry Fleuss and the Siebe Gorman company which was in the mid 19th century... AND Hans Hass was filming on a Drager SCR (a mature, tried and tested system) at about the same time as Cousteau and Gagnan open-circuit solution was being bench-tested.


One other thing... Chris isn't really that young either... LOL.

---------- Post added July 8th, 2013 at 04:58 PM ----------

I really believe there needs to be some other fail safe system for things that can kill you. Alarms, something, when the PO2 is getting too high or two low or you've packed your scrubber improperly...

The problem is that there are alarms for these things, Tracy... at least on some machines... but these oversights are not the "culprits" in many cases. For example, the standard agency advice to "Dive within the limits of your training and experience." are too often ignored with tragic consequences.

 

[gianaameri]

Not really. First Open-circuit scuba is generally accepted to be the AquaLung invented in early 1940s.

First rebreather is generally accepted to date from the patent for Henry Fleuss and the Siebe Gorman company which was in the mid 19th century... AND Hans Hass was filming on a Drager SCR (a mature, tried and tested system) at about the same time as Cousteau and Gagnan open-circuit solution was being bench-tested.

Some person after the people you mention decided to add a galvanic O2 sensor to a rebreather to dive it deeper and longer... this was not exactly a very smart thing to do and that is when the bigger problems started.

That - the addition of the galvanic O2 sensors to a rebreather - is a young and very dangerous technology to an otherwise older tool.

Do you know who had such a bright idea (to add a galvanic O2 sensor and electronics to a rebreather) and exactly when and what were the results of the initial experimentation?

---------- Post added July 8th, 2013 at 04:36 PM ----------

They also issue a "wreck" cert but anybody who does a significant penetration with one has a death-wish.

I do not think PADI issues a wreck penetration card. Never heard of it.

I have a PADI Dolphin SCR C-card (and a host of other PADI C-cards) and the course and instructor were very good.

---------- Post added July 8th, 2013 at 04:45 PM ----------

Oohs super secret documents!

Yes, correct.

A good portion of the documents have been made secret by the U.K. authorities.

They tried very hard not to disclose the information and a substantial portion of the documentation remains secret and not accessible.

I suspect that they will try very hard to disclose as little as possible to anyone making a FOI request same as they did with me.

Why?

I don't know what else is there to know, but what I know, you know.

 

[Chris Brown Tech]

One other thing... Chris isn't really that young either... LOL.

You beat me to it again!

I was just about to point that out

 

[gianaameri]

You beat me to it again!

I was just about to point that out

Looks pretty young to me at this link: CONTACT

 

[TSandM]

Nobody is ever going to be able to prove whether one is safer than the other, because to develop an incident occurrence statistic, you have to have a denominator, and we don't have it. Even if we had some data, we'd argue about whether number of divers was adequate, or whether you had to adjust for the increased HOURS in the water spent by people on rebreathers.

My completely non-scientific take is that I read everything I can get my hands on about diving fatalities, including belonging to a diving accidents group. Every year, I hear about fewer than a dozen OC deaths, a couple of cave diving deaths, and a couple of rebreather deaths. Given that the number of people doing OC recreational dives has to be at least an order of magnitude greater than the number of people doing cave dives or diving rebreathers, I conclude that the latter two are higher risk than the former.

I am not saying, and have not said that the units themselves are failing, in the sense of having been properly prepared and tested and then killing people during a dive. I do believe that the interface between machine and operator is substantially imperfect (this is true of OC as well) and that where it fails, fatal accidents happen more often than fatal accidents happen when people fail to service, monitor, prepare or test their OC equipment.

 

[Atom]

What is boils down to is what is the Safety Integrity Level of the overall system (taking into account the Safety Integrity Level of each subsystem) AND taking into account the interaction between the man and machine (that is factoring in the Human Error and design the unit to take into account for that).

The current machines fail miserably in taking into account the Human Factor in the design (and then manufacturers blame the human for the failure).

Current machines can be improved at the design level to reduce the risk of human error (and this won't cost much at all).

Then there is the bigger issue of the Safety Integrity Level of the electronics.

In the current machines available to the general public it is "less than SIL 1" (which means they do not meet the "Functional Safety" standard).

That is what apparently current technology cannot overcome. Manufacturers can't deliver currently machines with a SIL level of at least 1 or above.

We need a new technology where each sub-component and the assembled unit will be at least SIL 1 or above to meet "Functional Safety."

Till then, it is Russian Roulette.

You are just going to fool yourself into believing that if you are diligent and do everything right you will live on rebreather.

If the SIL Level is too low (meaning the Probability of Failure of the machine is too high) - even if you are diligent and do everything right you will eventually die on rebreather.

Of course if you then use galvanic O2 sensors which are older than 18 months as in Wes Skiles unit, you dramatically increase your chances of dying on an already very dangerous machine.

Some people asked what "Functional Safety" or lack thereof means. I posted earlier some references to articles explaining it in relatively simple terms (you'll need to do the reading).

Until you can give at least a few concrete examples of what need to be modified and how the units are failing at functional safety this is all generic complaints about a somewhat vague and complex standard. Can you be more specific?

 

[flots am]

Until you can give at least a few concrete examples of what need to be modified and how the units are failing at functional safety this is all generic complaints about a somewhat vague and complex standard. Can you be more specific?

It needs to work like an appliance that has received a UL rating.

This means that even if you screw up, it needs to fail in a safe mode, not a catastrophic or fatal mode.

Specifics are irrelevant. It needs to have no failure modes that are less safe than an air delivery failure on OC.

flots.