Rebreather Discussion from Brockville Incident

[doctormike]

Chris, I very much appreciate your expertise and experience. You are far more of a diver than I will ever be, and I don't mean to seem disrespectful. But I have know Lynne for a long time, and she is always a cautious voice of reason on this board, and a very experienced diver as well.

I have been following this thread, and while I understand your frustration, you should know that none of this is making this OC diver feel more comfortable about considering CCR. When the CCR proponents are listing the number of friends they have that have died while diving a rebreather (I think almost 10 in this little thread alone, including one of mine), that doesn't make me think that "CCR is just as safe as OC".

Yes, it all comes down to comparing equivalent dives, and screening out the effect of CCR being used on more aggressive dive profiles. But I think that you are missing the main point. No one is saying that a rebreather is a time bomb on your back, waiting to fail and kill you. We are saying that the inevitable human error is more likely to kill you on CCR than on OC. When a device reaches a certain level of complexity, then that by itself is a safety issue if the device is meant to be used by a human being, no matter how bulletproof the machine is, no matter how well trained the operator. And when one well known mode of failure is that it renders the operator unconscious, that really puts this particular machine in a category of it's own. As was pointed out upthread, the failure modes of OC are different than the failure modes of CCR.

So while maybe the extra gas time will help in a few situations (entrapment or entanglement), it's still not clear to me that it's a wash, that the extra risk of CCR diving is balanced by that advantage.

I think that if you present CCR as a calculated, carefully mitigated additional risk (just like technical diving), rather than denying the additional risk, then it would come off as less defensive.

 

[TSandM]

Chris, I understand there is a lot of misinformation and sometimes almost hysteria around rebreathers (and you can read some posts here that are sort of that way).

But I cave dive, and I will freely admit that cave diving is higher risk than recreational (or possibly even moderate technical open water) diving. Cave diving, like rebreathers in some ways, requires a mentality that is very meticulous, develops a routine and sticks to it, and is unwilling to tolerate even small deviations from acceptable functional status at the beginning of a dive. A lot of cave diving deaths result from people who have failed in one or more of those areas.

Rebreathers, I think, because of the complexity of the systems and the number of failure points, require a similar meticulous approach and a VERY risk-averse attitude, where the diver doesn't look a minor problems and say, "Well, it shouldn't be like this, but I'm going to dive it anyway."

Where a system is that complex and that demanding of the operator for safety, I think you just HAVE to admit that it is a higher risk system. Cave diving is higher risk, and the training is designed to weed out the folks who don't fit the profile (and isn't always successful in doing that). I worry about the push to get rebreathers into the general recreational diving population, because I think the same scrutiny won't be applied to the people who are buying the recreational units, on the theory that it's recreational diving, how risky can it be? The problem is that, unlike OC (at least in all but the strangest circumstances) a rebreather can kill you in four feet of water, and the failure modes that can do that are no less likely to occur on recreational dives than they are on technical or overhead dives.

 

[Doppler]

I would like to reiterate the question already asked: Why are rebreather folks so defensive?

I give you a similar answer to the one I gave to Ayisha in a private message: I am not sure "rebreather folks" are being defensive at all. The rebreather community -- the manufacturers, instructors and users -- HAVE set a pretty good example to the diving community as a whole, what should be done in the case of a serious incident with a rebreather. I posted a link to one example and Martin's publication of this was in part a response to Rebreather Forum 3.0 which had safety as its focus.

What is difficult to stand by and say nothing about are unsubstantiated claims by self-proposed experts who write that Rebreathers are death traps and other silly bull****. This is especially annoying in light of the massive amount of data that speaks to reasons that are far more concrete and very simple to fix.

I would not and have not said that rebreathers are safe, because nothing about diving can be said to be safe. I might get bent like a prezel next time I get into the water. BUT within the parameters of the remit due to us from ANY company building dive gear, it seems to me that CCR manufacturers are responsible, and the products they produce are fit for purpose..

Someone dies on a CCR, and it seems that the first thing that everyone does is blame the unit when the evidence indicates that in the VAST majority of cases, it's the user who is to blame. NOW you might say: Well, that just proves that CCRs are poorly engineered... I suggest it proves nothing of the sort, since you cannot design a unit that will prevent some poor sod from ignoring his training or the operational limits of the machine and killing himself.

 

[gianaameri]

Back to my original point - lets see an fatality caused by the machine.

See my post 109.

 

[Chris Brown Tech]

Chris, I very much appreciate your expertise and experience. You are far more of a diver than I will ever be, and I don't mean to seem disrespectful. But I have know Lynne for a long time, and she is always a cautious voice of reason on this board, and a very experienced diver as well.

I have been following this thread, and while I understand your frustration, you should know that none of this is making this OC diver feel more comfortable about considering CCR. When the CCR proponents are listing the number of friends they have that have died while diving a rebreather (I think almost 10 in this little thread alone, including one of mine), that doesn't make me think that "CCR is just as safe as OC".

Yes, it all comes down to comparing equivalent dives, and screening out the effect of CCR being used on more aggressive dive profiles. But I think that you are missing the main point. No one is saying that a rebreather is a time bomb on your back, waiting to fail and kill you. We are saying that the inevitable human error is more likely to kill you on CCR than on OC. When a device reaches a certain level of complexity, then that by itself is a safety issue if the device is meant to be used by a human being, no matter how bulletproof the machine is, no matter how well trained the operator. And when one well known mode of failure is that it renders the operator unconscious, that really puts this particular machine in a category of it's own. As was pointed out upthread, the failure modes of OC are different than the failure modes of CCR.

So while maybe the extra gas time will help in a few situations (entrapment or entanglement), it's still not clear to me that it's a wash, that the extra risk of CCR diving is balanced by that advantage.

I think that if you present CCR as a calculated, carefully mitigated additional risk (just like technical diving), rather than denying the additional risk, then it would come off as less defensive.

Sorry Mike, my comments werent directed at you. There were other posts that suggested I was being naive. Plus the main thrust of my latest post was in response to the general comments on here an on hundreds of other posts across the net. Hope you didnt think I was responding to you specifically.

Im not denying any risk. Nor am I saying its safer than OC. My post clearly states that there are no generalisations to be made. I dont want you to feel more comfortable about diving CCR as I dont know your diving experience or skills. I totally accept that CCR isnt for everyone.

My arguments are more about dispelling common myths and inaccuracies than being defensive or flying the ccr flag or tying to get everyone into it. Im saying that you cant state CCR is more dangerous than OC. Too many variables, and not in every case and not for everyone.

I get your tightrope analogy, but I still dont think its comparable, sorry Yes, you can die on a CCR n 4 feet of water. Yet we still have OC instructors with DSD fatalities in pools dont we? In one case study, the student could have stood up and they would have been in fresh air. The group was directly supervised by dive professionals. People die on scuba in pools, shallow water and deep water. In fact, many diving fatalities happen on the surface.

---------- Post added July 8th, 2013 at 09:39 AM ----------

I think you just HAVE to admit that it is a higher risk system.

No. thats my point. Not in all situations, for all people. Me in a cave on OC doing a simple 1 stage penetration would arguably be more dangerous than me doing it on CCR as Ive never been in a cave on OC.

I put this over on CCRX. It depends on the individual and the environment in which they are placed. Experienced cavers with more experience on OC than CCR tend to favour OC for the majority of their cave dives and rightly so. I favour CCR as I have zero OC cave experience. Which is safer for me? Does it change when you put me in a cave I dont know versus one I do?

Heres another example: I could put a non diver on a rebreather in a pool with 50% DIL and a non diver on OC in the same pool. Which is safer? Very difficult to categorically state one or the other.

Why do people want to make these general statements in diving such as "of course you have to say CCR is more dangerous than OC" It simply cant be proven

---------- Post added July 8th, 2013 at 09:51 AM ----------

See my post 109.

The voyager is not a commercially available unit certified to the 'flawed' CR standard that you are fond of quoting. That was a boutique machine, not in any state of volume production and shouldnt be considered in the context of these debates as it is a) Not available for purchase b) Not a unit that the main agencies offer training on and c) has no market penetration or any significant number of units in general use today.

If we want specifics:

JJ, Meg, Inspo classic, Inspo & Evo Vision, PRISM Topaz or Hollis PRISM II, CIS-Lunar MK5, Boris, Sentinel, Poseidon MKVI, Titan, Optima, Pathfinder, KISS classic or Spirit, rEvo 1,2 or 3, mccr or eccr hybrid, Hammerhead, Pelagian, ( not sure if nautilus or submatix would qualify as currently available and commercially produced, Id have to take advice)

Lets have the specifics of the fatality on any of these units (there are hundreds to choose from unfortunately) that you feel is an example of death by unit for discussion please

 

[gianaameri]

I put this over on CCRX. It depends on the individual and the environment in which they are placed. Experienced cavers with more experience on OC than CCR tend to favour OC for the majority of their cave dives and rightly so. I favour CCR as I have zero OC cave experience. Which is safer for me? Does it change when you put me in a cave I dont know versus one I do?

OC is always safer than CCR irrespective of the environment or user because:

1. OC is a well tested and tried technology.
2. OC fully meets internationally recognised standards (EN250)
3. OC is less complex and has less failure modes.
4. OC failure modes do not render you unconscious and incapable of self-help.

Now, I use a CCR for Cave Diving (and only some Cave Dives, but not all), but that is because logistically it is easier for me.

I'd rather prefer to do the dive on OC, but then I would need 10 Sherpas to stage bottles and carry equipment in and out of the cave.

I am talking about long penetrations and long dives on scooter for several consecutive days of diving. For short penetrations to say 300 meters if the depth does not exceed 30 meters, I'd definitely not use a rebreather, but go OC.

Some people mentioned in another post that a CCR will give you a longer time to sort yourself out in case of a collapse.

Man, what a non-sense.

In case of a collapse reality is - you are done!

See: Cave explorer found dead after dramatic eight-day search - FRANCE - FRANCE 24

We have pre-agreed locations in the cave where there is a known dry section as a meeting point (i.e. to await rescue), but if your way is blocked by a fresh collapse to either the exit or a safe heaven you can pretty much forget digging your way out of the collapsed way.

Rebreather has its advantages in terms of reducing costs (i.e. for deep He dives) and logistics (only the O2 and scrubber need refilling while on OC you need to take out of the cave and refill lots of botttles), but it is a far bigger risk than doing the same dive on OC.

 

[Chris Brown Tech]

OC is always safer than CCR irrespective of the environment or user because:

1. OC is a well tested and tried technology.
2. OC fully meets internationally recognised standards (EN250)
3. OC is less complex and has less failure modes.
4. OC failure modes do not render you unconscious and incapable of self-help.

1 - So are CCR's. Thousands of dives, thousands of hours.
2 - The Rebreathers on my list reach the internationally accepted standards. Even if they didn't, it doesnt necessarily mean they are unsafe.
3 - Complexity is relative and as per my other posts. It depends, depends, depends. A well trained CCR diver on an mCCr would likely find it less complex than a poorly trained, inexperienced OC diver in a dry suit on their first 100' dive with a pony bottle, smb and reel.
4 - SOme of them do. Running out of air, CO, breathing the wrong gas etc. I dont know the per capita rates, but many divers have lost their lives or become injured from breathing contaminated gas or gas with the wrong levels of oxygen or gas with carbon monoxide or toluene in it.

Please explain why any of the above categorically confirms OC is safer?

Can we also have an example of a fatality caused by a rebreather on my list please.

 

[MalibuJerry]

OC is always safer than CCR irrespective of the environment or user because:

1. OC is a well tested and tried technology.
2. OC fully meets internationally recognised standards (EN250)
3. OC is less complex and has less failure modes.
4. OC failure modes do not render you unconscious and incapable of self-help.

Now, I use a CCR for Cave Diving (and only some Cave Dives, but not all), but that is because logistically it is easier for me.

I'd rather prefer to do the dive on OC, but then I would need 10 Sherpas to stage bottles and carry equipment in and out of the cave.

I am talking about long penetrations and long dives on scooter for several consecutive days of diving. For short penetrations to say 300 meters if the depth does not exceed 30 meters, I'd definitely not use a rebreather, but go OC.

Some people mentioned in another post that a CCR will give you a longer time to sort yourself out in case of a collapse.

Man, what a non-sense.

In case of a collapse reality is - you are done!

See: Cave explorer found dead after dramatic eight-day search - FRANCE - FRANCE 24

We have pre-agreed locations in the cave where there is a known dry section as a meeting point (i.e. to await rescue), but if your way is blocked by a fresh collapse to either the exit or a safe heaven you can pretty much forget digging your way out of the collapsed way.

Rebreather has its advantages in terms of reducing costs (i.e. for deep He dives) and logistics (only the O2 and scrubber need refilling while on OC you need to take out of the cave and refill lots of botttles), but it is a far bigger risk than doing the same dive on OC.

Factually incorrect. At 300' in a current on OC you have very limited time to take care of a problem, say an entanglement, relative to CCR. There are circumstances where CCR is the proper tool, and others when OC is the proper tool. To make a categorical statement like this illustrates a lack of knowledge about rebreathers and their effective uses.

 

[gianaameri]

The voyager is not a commercially available unit certified to the 'flawed' CR standard that you are fond of quoting. That was a boutique machine, not in any state of volume production and shouldnt be considered in the context of these debates as it is a) Not available for purchase b) Not a unit that the main agencies offer training on and c) has no market penetration or any significant number of units in general use today.

PADI issued C-Cards for the Voyager.

I agree with you it was/is crap, but I could say the same for some of the rebreathers you list as well (and none can achieve the "Functional Safety" mandated by the standards which many instead claim to meet).

Now Chris, I think you are young and passionate, and a good instructor, but your passion for rebreathers is clouding your judgement.

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

Dive safe!

---------- Post added July 8th, 2013 at 01:56 PM ----------

Factually incorrect. At 300' in a current on OC you have very limited time to take care of a problem, say an entanglement, relative to CCR. There are circumstances where CCR is the proper tool, and others when OC is the proper tool. To make a categorical statement like this illustrates a lack of knowledge about rebreathers and their effective uses.

In my example nowhere I mentioned 300' (I said 300 meters [linear] penetration at 30 meters max. depth).

Entanglement are quick and easy to fix (bigger problem for the mind to deal with it than they actually are). CCR has some, but a very limited advantage over OC in an entanglement (current or no current).

As a matter of fact, in a current I would not dive a CCR at all (if given a choice). I hate CCR in a current or where any hard work is involved.

CCR is useful from a gas consumption stand-point because on CCR you can do in a cave the equivalent of "recalculating thirds" without exposing yourself to the risk inherent in recalculating thirds whilst OC diving. As much I give you.

 

[tracydr]

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.

---------- Post added July 8th, 2013 at 12:34 PM ----------

You are a CCR Instructor, so you should know (or could just ask the manufacturer if you don't) for the rebreathers you teach/sell if they meet Clause 5.13.1 of EN14143:2003.

All it will take you is an email to the manufacturer (no need to ask the U.K. Secretary of State ) and then you can let us know if you are still unconvinced.

I am not releasing any documents on an internet forum.

Oohs super secret documents!