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A post mortem has concluded that an excessive build-up of carbon dioxide caused the black-out and death of rebreather diver Dave Shaw. The Australian died deep in a cave while trying to raise the body of another diver.

Shaw, 51, was trying to recover the body of Deon Dreyer, a 20-year-old who disappeared while diving in South Africa's inland Boesmansgat Cave in 1994. The operation was carried out at 270m - far deeper than any previously attempted working dive, outside commercial dives using recompression bells.

In addition to a bodily examination, Shaw's equipment was inspected and his gas mixtures analysed. Investigators even re-enacted his breathing patterns, based on footage from Shaw's video camera. This showed that his breathing became increasingly laboured before stopping.

It was seen that Shaw started work to free Dreyer's body but, as pre-arranged, aborted the effort when he had not succeeded after six
minutes. Ascending, he became entangled in the line previously used to mark the body. While attempting to free himself, he stopped breathing about 22 minutes into the dive.

The forensic report has been published by the International Association of Nitrox and Technical Divers.

"Overfilling of his re-breather appears to have prevented him from exhaling properly," the report states. "The breathing impairment, combined with the increased activity of recovering the body, led to a critical build-up of carbon dioxide over a period of 10 minutes. This is sometimes called
Œdeep-water black-out¹.

"David became increasingly incapacitated, eventually lost consciousness and ultimately drowned. While relatively swift, the duration of the process
favours carbon dioxide build-up as a cause rather than a lack of oxygen."

The report adds that an element of nitrogen narcosis may have "significantly interfered with his ability to solve the problem before it was too late".

"Calculations suggest that he may have experienced the narcotic equivalent of a 44m dive on air, but this would have been compounded significantly as the carbon dioxide levels rose," it says
 

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I saw the video last night from Daves helmet cam of his last moments - man I needed a beer (or ten) after viewing that.

I pressume they mean overfilling of the scrubber and not the CL as the OPV is very light on the MK15.5.
 

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Where did you see the video? I've had a look around the net but can't find it.

Poor bloke, RIP.
 

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Where did you see the video? I've had a look around the net but can't find it.
I should bloody well hope not. Its not some snuff video FFS.
 

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more weaselly than a weaselly thing
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Lets leave this one here, shall we. Dave's loss is tragic and unfortunate, but hopefully some accident analysis may help others.
 

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Tek & RB Instructor: fluent in 'Franglaise'
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wreckweasel said:
Lets leave this one here, shall we. Dave's loss is tragic and unfortunate, but hopefully some accident analysis may help others.
I agree, perhaps this a thread that can now be closed by one of the mods?
 

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Thread closed on request.

RIP Dave.

Daz
 

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Dave Shaw/CCR CO2 Buildup

The more I read about Dave Shaw and what happened in Boesmansgat, the more the circumstances of his death seem strange.

I know that they blamed it on CO2 buildup due to him having to exert himself whilst movng Deon Dreyer's body and freeing himself from the cave line, but surely if there was an excessive CO2 buildup in the loop, his sensors would have read it and either injected more 02 or sounded the buzzer so he could do it himself?

As you can tell I don't know much about CCRs, just bits and bobs that I've read, so I could be missing something obvious, it just makes it hard to believe that's all that went wrong when you read about some of the other situations he's got himself out of. When diving at Komati he not only became tangled in the line a couple of times at 140m but also had an electronics failure and had to go to semi-closed operation at 105m. Was it just the extreme depth that made the Boesmansgat situation end very badly eg increased narcosis and less time to sort things out?
 

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As a pretty unaquainted non CCR diver myself I beleive that rebreathers only have O2 sensors. These detect the PPO2 and the computer decides if its high or low. As far as I can tell, there are no CO2 sensors on the market which oe would beable to put in the circuit. I have even asked my Chemist buddy if he can get lipmus paper which detects CO2, but he can't, if such a thing exists. I imagine anyone developing a small cheep unit which one could 'bolt on' to a RB would soon capture the market..

I'm sure others on here will have nore on this.

Dave C
 

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I haven't done my CCR course yet and am not familiar with the specifics of this case, so I may be wrong, but with the Inspiration for example I believe there isn't a CO2 sensor, just oxygen sensors. A slow rise in CO2 often causes increased breathing and headaches. The CO2 rise would also not be solved by injecting more O2, and would need either a diluent flush (if scrubber is working) or more likely bail out to open circuit, since you would assume scrubber isn't working. The other point is that a SUDDEN rise in CO2 (exceeding design specifications of scrubber for CO2 removal at extreme depth for example) can cause unconsciousness with no warning so the poor chap may not have had time to react. This was proved by the Royal Navy in dry chamber dives during WW2.

As I say, I haven't done the course yet (hopefully to be done in April), so I may be talking bollocks......:)
 

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As others have mentioned, there's no generally available in-the-loop CO2 sensor at the moment. To understand how scrubbers work at depth, Gordon Henderson's description is a great intorduction (reposted by Rob Evans, post #7 at http://www.yorkshire-divers.co.uk/forums/showthread.php?t=4793)

From this you'll see that working hard at depth is the heaviest loading you can put your scrubber under, and the inquest reported that the scrubber was also over-packed, possibly increasing the work of breathing. CO2 hits are nasty things - the textbook symptoms of headaches and heavy breathing are severely compounded at depth, and people report symptoms including a sense of rising panic (I've been there) or a strange sense of detachment where they know they are having a CO2 hit but are unable to do anything about it.

Dave Shaw had undertaken that dive with a specific purpose, and he gave his life trying to get the job done. Sure, we can discuss the mechanics of CO2 hits but any discussion of Dave's death without access to all the facts is at best speculation, at worst totally insensitive to the loss suffered by his friends and family.
 

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Makes you wonder how much use a CO2 sensor would be. By the time it trips the alarm you'd probably be incapable of doing much about it. Some people are natural CO2 retainers too so the baseline would be highly variable.

I've started freediving training recently and it made me think about CO2. Some of the exercises are designed to increase your tolerance to both high CO2 and low O2 levels in the blood. I'm wondering if this is beneficial or counterproductive to diving my RB as it is over-riding natural warning signs.
 

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NotDeadYet said:
Makes you wonder how much use a CO2 sensor would be.
quite a lot, in a fully Eccr, you could easily have a solenoid for diluent and loop opv and have the system flush the loop repeatedly. if done correctly, this would be almost an auto switch to O/C

you might need better than 2L cyls though ;-)
 

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Violent Ken said:
I know that they blamed it on CO2 buildup due to him having to exert himself whilst movng Deon Dreyer's body and freeing himself from the cave line, but surely if there was an excessive CO2 buildup in the loop, his sensors would have read it and either injected more 02 or sounded the buzzer so he could do it himself?
Others have commented that there is no CO2 monitor but more and more on CCR we see CO2 as the demon that is out to get us. At serious depth the results are similar to an oxygen hit and surviving a blackout on scuba gear is not common. Surviving it at 270m, over 50m deeper than your next support diver, is not going to happen.

Many of the early fatalities, in retrospect, look like CO2 build up just switching off the diver's ability to cope with a problem so now the emphasis on good packing, sealing and being conservative with the scrubber are emphasised and re-emphasised. Rebreathers are proliferating with thousands of Inspirations out there and new models, seemingly, every month but the casualty rate is falling. Perhaps we are learning things.

Dave Shaw was pushing the system to its limits and the laws of statistics got him. If it had been on a record attempt we might be less sympathetic but he was going back to a depth he had already done to do something for another diver's family. It's a better obituary than most.
 

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new....

Hi guys, new to the list but have tried to follow the thread on dave's death...The " official " cause is actually the right one..overbreathing ( co2 build up), getting caught in the line ( at 6 min bottom time -trying to get out). Deon's Body was also neutrally bouyant, not a skeleton as expected and this caused the body to move underwater, something tottaly unexpected.
BTW don't believe all that you see in the press...please ?
We are currently having a serries of talks on the Dive in SA ( no, we are not charging for it !) to settle the rumours and tell the facts. I will gladly tell what I know. I was involved with the dive from the begining and Dave was a personal friend.fire away...
 

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BigB said:
Hi guys, new to the list but have tried to follow the thread on dave's death...The " official " cause is actually the right one..overbreathing ( co2 build up), getting caught in the line ( at 6 min bottom time -trying to get out). Deon's Body was also neutrally bouyant, not a skeleton as expected and this caused the body to move underwater, something tottaly unexpected.
BTW don't believe all that you see in the press...please ?
We are currently having a serries of talks on the Dive in SA ( no, we are not charging for it !) to settle the rumours and tell the facts. I will gladly tell what I know. I was involved with the dive from the begining and Dave was a personal friend.fire away...
BigB,

It would be good for you to share the facts as you know them, perhaps others can learn from what happened.

As for the loss of your friend, please accept my condolences and those of the others on this list, whom I will take the liberty of representing with this comment.

Regards

Dave Cooper
 

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Tanks Dave,

don't do this list thing so if protocol is wrong please shout...

Dave did this dive for himself, no financial gain, the sponsors were Afrox ( African Oxygen) for gas and that was it. they sponsor most deep record attempts in SA.Did Nuno Gomez's ( he is Portugese South African btw and not polish as elsewhere metioned..) dive as well as Verna's.( woman deep record OC).

Everybody's accomodation was paid for by Theo Dreyer, Deon's farher. All the other "amatuers" was asked by Dave to "volunteer" and paid their own way.

Dave offered the dreyer's the option to find closure, they accepted and offerd to pay for the accomodation. this was an adventure for Dave and for all of us, this dive was always an attempted recovery. Dave did it for the hell of it and to be the 1st person to have bottomed Boesmansgat twice and do a repeat world record. No other reason. He paid Gordon Hiles ( surface video) and Derek Hughes ( surface stills and UW video ) to record the dive with the aim to have a documetary made. He (Dave) paid for the helmet camera and the camera Housing.

Boesmans is not accesible with a bell. the entrance is slightly wider than me ( pretty wide but still no bell..) the cave is 271 m long by 61 m wide.

The police divers were there because Deon's docket had not been closed.They also had the police chamber on site and manned it ( thank God !!)Their max was 22 m within the light zone and never away from the shotline. they did the donkey work, carried cylinders and helped pull the line out on the last day. they were the best guys I have ever had the pleasure to work with...

Rescue scenario's were practised two days before the dive.The 911 paramedics were just that..Paramedics.Their job was to stabalize the patient at the bottom of the hole ( 40-50 m deep) before he was to be hoisted to the surface, they did not need to be boffins on deco sickness. the Boffin, Jack Meintjies, was on site, at the top by the chamber.He was in telephone contact with Frans Cronje, an even bigger Boffin, throughout the dive and the ensuing rescue of Don Shirley.

This is getting a bit long...will stop here and carry on if there is interest, don't want to clogg your forum. I will accept private mail or skype chat but prefer to do this openly so everyone gets the true facts...1 thing I think we owe Dave.
tanks...
 
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