Comprehensive list of all accidents

Freef

Thanks for clearing that up, Alex.

__________________
David.

Currently owner of two differently sized ankles.

Tom Mount

Dr M
I do not comment often in thisare but yourstament leaves me a little shocked- I image I dive diferently than you in some aspects so take offense at the "
"and some peoples backs are up? tough tittiesthey will be dead soon anyway

well one of them will be next month, and one the month after that and another after that and so on until something radical happens."

I'm differnt than you and hate to have aforecase I will die due to that my first rebreather dive was most likely before most on this list were born and still kicking.

So get back to real talk again
Tom thousands of CCr dives and plan to stay alive to talk about it

AD_ward9

Hi Gill,

Your questions are very good, but the data is not good enough to identify all this just yet. However some things are clear already: see below.

Just as a first pass, of the 150 accidents we have now verified, around 32 are general SCUBA accidents, around 118 are equipment failures.

Equipment failures are of 3 causes:

1. Failure to maintain O2 within reasonable bounds (majority of the cases)
2. Failure to keep CO2 within reasonable limits
3. Failure to keep the water out

The general SCUBA accidents include root causes of marine life, underlying illness while diving, human error common to OC, entanglement etc.

The equipment failures are only where the root cause was hypoxia, hyperoxia or hypercapnia, but excludes cases where the user did not turn on their O2 (we treat this as human error, just as we do the a poacher who put air on a Dolphin instead of Nitrox because he had never trained for any rebreather).

The have an outstanding piece of work by Dr. Dick Van at DAN and his colleagues, from the analysis of 947 O.C. SCUBA accidents. From this we know the incidence of sudden Loss of Consciousness occurs less than one per 3 million diver years. So we are treating all Sudden LOCs as equipment failure, except where the diver did not switch on the O2 (which I would call equipment failure, but most on this forum would not, or cases like the poacher I mentioned above). I believe this paper will be published shortly for us all to share.

I have been at The Dive Seminar (Bergen) this week. Discussion with Dr. Phillip James confirmed again a sudden LOC just does not happen in commercial diving, so unless there is a strong indicator of an underlying illness, such as diabetes, a sudden LOC should be treated as an equipment failure.

We have been advising rebreather manufacturers of this, and the algorithms needed to avoid these 3 root causes of fatal accidents. In short these are:

O2:
Switching on automatically with falling PO2
Calibrating O2 sensors on air only with an auto check on pure O2, do not cal on pure O2.
Do not allow users to use anything other than 99.5% O2. Too many fools do not realise that the other % is argon, and that argon builds up and then anaesthetises the diver.
There should be a truly independent PPO2 monitor on a rebreather using at least 3 cells.
Ensure solenoid is as close as possible to O2 cells.
Do make some effort to comply with EN61508, so the processor does not hang, jump or contain single points of failure. I am fed up of seeing handsets that go out of dive mode to a non-dive mode when there is a brown-out.
Remove primary cells
Sort out the power supplies so that handsets and CCR controllers do not suddenly fail when there is a brownout or battery low condition.


CO2:
Remove temperature sticks
Label scrubbers with CO2 scrubber limits based on 1.6l/min
Bring WOB to within the EN14143 limit with a used scrubber.
Size the hoses to at least 36mm I.D. and the mushroom valves to equivalent to a 32mm ID pipe.

Floods:
Eliminate the common causes for floods (poor keying, poor seals).
Warn of the spasm effect that will result from using lime.

SCRs:
All SCRs should have one cylinder of gas only (no provision for a second cylinder) and need a twin orifice with a clear label that the orifice flow must be measured before every dive.

The above issues are facts. I am not going to distract this thread debating them (I am sure yourself Gill will appreciate this, but for the sake of others I should point out that our role is not to educate the world but just ensure that Rebreather manufactures have the facts to avoid major safety blunders: if they want the details then any decent expert should be able to give them that).

Any more detailed data that this really has to wait until the panel that has been assembled completes their review.

On your point of mods, only a genuine guru or a fool would modify a rebreather. Companies offering mods should put them on the equipment themselves then warranty the mod.

When we (at DL) get an Rebreather into test, we remove all accessories: even the balance weights and crotch straps unless the RB manufacture has provided them. One thing this has done is reinforce to us the lamentable state of some equipment when it leaves the factories. Divers should not have to put cam bands onto DIL cylinders to attach weighs, nor should they do any other change unless they are prepared to test it as thoroughly as a competent manufacturer. Manufacturers need to ensure the equipment is ready to use and has reasonable levels of safety when it goes out.

Alex

silent running

Hi Alex, it appears that I may be one of these fools as I do most of my diving in the Pacific with O2 that is sometimes less than 99%. So far, I have not seen less than 95% and so far, I'm still kicking. Oh, and I usually spend 4-5 hrs a day in the water and dive for at least a week straight.

I don't mean to take this lightly, but it seems that many CCR divers regularly dive with O2 which is less than 99%. Do you know of any deaths artibutable to argon contamination of O2? And if so, any idea of the % found in the O2 supply?

I may be missing something, but as long as the fraction of argon is small and given that the O2 injects will happen most frequently on ascent as the PP of argon is dropping, isn't a very small fraction tolerable in the loop? Thanks, -Andy

Hanssing

This should perhaps be taken to another thread?

The Argon will build up in the loop, since the say 1.0 l/min injection will conntinously add 0.05 l/min Ar @ 1bar, so unless dill-flush is regularly performed you WILL have a buildup of Argon. Ie. even during the divephase, you will have an PPAr thats slowly creeping upwards.

OVer an hour you would get 0.05l/min*60min=3l@1bar in the loop. Say total loopvolume is 7l and youre at 30msw => FAr = 11%, PPAr = 0.4bar

Keep flushing the loop......

Nicolai

__________________
Woohooo - I can change my rEvo!
Its going to be bitchin' tricked out piece of gear

dave t

O2:
Switching on automatically with falling PO2
Calibrating O2 sensors on air only with an auto check on pure O2, do not cal on pure O2.
Do not allow users to use anything other than 99.5% O2. Too many fools do not realise that the other % is argon, and that argon builds up and then anaesthetises the diver.
There should be a truly independent PPO2 monitor on a rebreather using at least 3 cells.
Ensure solenoid is as close as possible to O2 cells.
Do make some effort to comply with EN61508, so the processor does not hang, jump or contain single points of failure. I am fed up of seeing handsets that go out of dive mode to a non-dive mode when there is a brown-out.
Remove primary cells
Sort out the power supplies so that handsets and CCR controllers do not suddenly fail when there is a brownout or battery low condition.


Alex what does that mean?

thanks

Dave

Ant Slegg

Two questions on the general principles:

1) Putting aside deaths per unit type is there sufficient data to "normalise" the data with respect to OC fatalities per year. I.e. is diving getting "safer", how does it compare with tech diving?

2) There are a significant number of British Isles incidents on the list.
Has anyone contacted the BS-AC to try and fill in any blanks?
I.e. BRIAN CUMMING at HQ who generates:
Annual Diving Incident Report - BSAC
Referring back to (1) above it the above report for 2006 (not 01-Jan to 31-Dec) has 3 out of 16 fatalities on rebreathers.

3) Is there any reason for the change in the file name being used?

__________________
Ant' S
Learning to dive since 1990...

AD_ward9

Hi Dave,

A primary cell is a non-rechargeable battery.

It is incompetent safety practice to run an unstable life critical system like a rebreather on battery that the user has select and to replace frequently. The reasons are:

1. Primary cells differ from company to company, and from batch to batch. User replaceable means the factory making the rebreather has no control whatsoever over what is actually powering the unit. That is an incompetent practice (I am being accurate here, not inflamatory).

2. Primary cells mean contacts. Contacts are unreliable. One does not put contacts in series with a power supply in a life critical system. One cannot: their MTBF adds directly to the MTBCF, and their MTBF is poor.

3. The primary cells off-gas toxic compounds. There is a NEDU report on one company's batteries for example (one rebreather company's). Often these cells are in the breathing loop.

4. The primary cell is generally the sole power source for a controller. This is incompetent on its own, but compounding this, the cells are not characterised fully as there are too many different battery types to consider by a company using them. This means the manufacturer of the equipment can get surprises. For example, resistance can increase causing cycling of the controller on, then solenoid pulls down the supply, causing it to reset and go off, repeatedly. That can increase the O2 in the loop enough to cause CNS.

5. In another variant of 4, the cells can come down just enough to miss the brownout reset period, but enough for the controller to hang.

Users want secondary cells (i.e. rechargeable batteries). This can be a much safer option, when done properly. That is, secondary cells can meet the ALARP criteria, whereas a primary cell cannot.

Alex

AD_ward9

Answering the 2 questions in turn:
A 1: Yes there is sufficient data. Rebreathers are much more dangerous than Tech Diving. There was an analysis on this presented to the British Hyperbaric Society using the database by Dr. Stephen Johnson earlier this month.

Food for thought: BSAC divers manage to kill themselves at the same rate per 100,000 as PADI divers in the USA. BSAC are mostly UK, and diving involves a lot of deeper deco diving.

A2: Yes. More information to follow. The BSAC list is very sparse but you may have misread the information. BSAC do include most of the UK accidents.

Alex

Freef

Why no second tanks? Just to prevent bottom and deco gasses being used, or are you against the same mix in both tanks? If it's to prevent deco gas being used, what about the practice of switching dil gasses on deep CCR dives?

No provision for a second cylinder is also sticky, as you need to carry bailout, and the holder for that can easily be used for a second loop feed tank, especially with adaptors from Tecme and the like.

__________________
David.

Currently owner of two differently sized ankles.