View Full Version : CCR Video on HSE Site
IanStevenson
28-11-07, 11:55
Hi folks,
Not my incident, but thought this might be interesting.
Recently a Sky News diver using a rebreather suffered from CO2 poising underwater - fortunately he was successfully rescued and is fine. Unusually, the incident was filmed by the police ROV they were shooting footage of at the time. Sky have assembled a TV quality documentary on the incident using this footage.. The accident was (according to the HSE) caused by practices commonly taught on rebreather courses.
The documentary is obviously of potential interest to those diving rebreathers, but it also provides a fascinating insight into the anatomy of a diving accident and rescue. Especially interesting is the behaviour of a distressed and confused diver underwater, and the problems switching to bailouts. As such, I would recommend it as interesting watching to any diver.
The HSE have circulated this video (which is copyright free) to rebreather instructors, and have made it available on their website at:
http://www.hse.gov.uk/diving/video/co2video.htm
Cheers,
Ian
Lizardland
28-11-07, 12:57
The video has been making the rounds and I'm not entirely sure why the HSE are making such a big thing of it. The incident happened because the diver re-packed used lime into his rebreather. The HSE says this is a commonly used procedure but I've never seen anyone do it ever nor heard of anyone say they do it. It's got to rate as one of the stupidest things you can do with a RB.
I don't think it carries much of a safety message other than as a bit of scare mongering. I really don't get what the HSE are trying to achieve by sending it out to dive schools. I suppose the best thing that can be gotten from it is if your buddy is having a problem don't sit there like a pair of idiots staring at him.
I must admit, work has made me a bit cynical as to the usefulness of the HSE to start with so I'm not really their biggest fans.
Cheers,
Stuart
I'm not a RB diver (yet?) but I'd agree with Stuart on that one, this seems to be nothing more than user error.
i don't think its really a concern for the HSE, no more than someone operating a food mixer & chopping their fingers off.
however, since they are promoting it, anyone learning from it has to be beneficial.
The HSE comment that a number of divers interviewed carried out the same practice, Because this was what they had been taught in training, This seems to point the finger at the training syllabus of one of the dive organizations?
Not being a RB diver i don't know if this is true?
MadMajor
Well, what do all the RB divers say - were they taught to do the same thing or was it highlighted as a specific no no to tamper with partly used "Lime"?
If I am correct, the other problem here is that the "Lime" is a chemical agent for removing CO2 that lasts a certain volume of gas cleaning, or something like that. From that you can estimate an amount of time, or amount of time at depth, or some such that it will safely be "good" for.
Am i right in saying however there is no reading on the system to say when the "Lime" "runs out" or when the CO2 in the breathing loop goes above an acceptable level. That seems to be the classic rebreather problem in reports - divers overcome by increased levels of CO2 without them becoming aware of it.
Apart from replacing the Lime regularly, how do you check the Lime is okay before and during a dive. This guy didn't simply miss a CO2 reading that should have told him there was a problem?
TheMacallan
28-11-07, 21:08
Well, what do all the RB divers say - were they taught to do the same thing or was it highlighted as a specific no no to tamper with partly used "Lime"??
No! And I've never met anyone who has. Six years on the Inspiration.
If I am correct, the other problem here is that the "Lime" is a chemical agent for removing CO2 that lasts a certain volume of gas cleaning, or something like that. From that you can estimate an amount of time, or amount of time at depth, or some such that it will safely be "good" for.?
Yes it has a finite life.
Am i right in saying however there is no reading on the system to say when the "Lime" "runs out" or when the CO2 in the breathing loop goes above an acceptable level. That seems to be the classic rebreather problem in reports - divers overcome by increased levels of CO2 without them becoming aware of it.
Yes, CO2 kills a high percentage of rebreather divers.
No, there is no CO2 warning. (on any rebreather)
Apart from replacing the Lime regularly, how do you check the Lime is okay before and during a dive. This guy didn't simply miss a CO2 reading that should have told him there was a problem"??
You replace the lime depending on the previous dive history. No mystique, all well laid out in the manual.
I agree with stuart with regard the buddies! When you switch to a bail out that indicates a problem, whether you are getting the OK symbol or not and its time to bail out!
Also there appears to be police divers, were they watching the video feed from ROV, if so why werent they down helping?
Think the Lime issue obviously needs adressing but the buddy system in this instance is not ideal, but could have been worse had he been solo diving.
Yes, CO2 kills a high percentage of rebreather divers.
No, there is no CO2 warning. (on any rebreather)
Is there not a clue as to the next step in the development of rebreathers in your statement here?
Lizardland
28-11-07, 21:36
I suppose as it was media diving it came under the view of the HSE. And yeah I agree if someone stops and thinks then it's a good thing.
I agree with TheMac, I've never heard of anyone ever being told this, I've never met anyone who does it and no manufacturer recommends it. Depending on which bit of gossip you believe :D the instructor involved was investigated and struck off, if that's true then quite rightly so. Personally I'd like to see him prosecuted for such irresponsible behaviour but there you go.
Like TheMac also says, there is no way of predicting how much life is left in the lime. The reaction generates heat and there's a warm line which moves through the stack as the lime is used, at least one unit has a thermistor array to track the front's progress. How beneficial that is I don't know. When I was at Cranfield Uni they were doing research into it and found some bizarre temperature spikes happening as the lime was getting used up. There have been prototype CO2 sensors promised but there's nothing realistic available as yet. The real downside is that it doesn't take much CO2 to cause problems so I'm a bit sceptical as to how much use a sensor is.
I've had three CO2 problems and all three times it has been due to getting water in the stack. Most of the other incidents from people I know have been user error too. It's pretty hard for a properly assembled rebreather's scrubber to fail.
There is another situation where you can overbreathe the unit, if your breathing rate exceeds the speed at which the unit can remove CO2, the only way round that is to avoid exerting yourself. If you're trying to get down a shot in a running tide this is easier said than done. In situations like that I have gone to my open circuit bailout in the past.
The only real thing you can do to prevent it is to be very aware of your breathing rate and if it creeps up without any cause e.g. you aren't fighting a tide, then you have a problem. Again easier said than done. In one of the CO2 incidents I've had the simple act of changing from one mouthpiece to another was a massively stressful experience.
Cheers,
Stuart
You replace the lime depending on the previous dive history. No mystique, all well laid out in the manual.
That was basically what I understood to be the case, but nice to have it confirmed. All things being equal, and if there is nothing wrong with the lime (can there be anything wrong with the lime?) as long as you keep track and change it in good time you'll be fine - get it wrong and you have a major problem with little warning, other than, as Lizardland says, spotting the minor CO2 warning signs while suffering from the problem!
Have fun, I'll hold off on my order for a few years more - but then again I'm too scared to do deco diving! :o
For the less initiated than even me, the point of all this (to be confirmed by someone who actually knows!) is that you can keep the o2 level as high as possible for varying depths, avoiding oxygen toxicity problems, but using the maximum o2 levels to minimise gas absorption, maximising no decomompression limits and/or minimising any decomprssion requirements compared to open circuit - by a large degree. Oh, that, and you don't produce any fish scaring bubbles!
my tuppence worth on the vid appart from the obvious low budget and poor casting i,m not surprised it went straight to dvd there was no sharks or anything . seriously thou i,m still a bit wary of the rebreather stuff never had a go thou
I suppose as it was media diving it came under the view of the HSE.
i don't believe that rebreathers can be used for commercial diving media work unless they fall in to the DWR 1997 (diving at work regs) & covered by an ACOPS (approved code of practice).
to the best of my knowledge, only the navy, army & police divers are covered by DWR 1997 in the use of rebreathers & are the only organisations to have the approved qualifications.
i have just had a look at the DWR & cant find any info to support rebreather diving other than commercial rebreather dive instructors.
was the man from sky a policeman...
was the man from sky not getting paid...
was the man from sky breaking the law right under the noses of... :)
TheMacallan
29-11-07, 07:47
Other ways to get a CO2 hit. Inspiration specific.
1) Use the counter lungs as a BC. (easy to do and creates loads of other problems).
2) Do not fit the Scrubber O ring.
3) Do not grease the Scrubber O ring. Common sense?
Straight form my six year old manual......
"Warning The O ring which fits between the cartridge and the pressure ring prevents CO2 in the expired gas bypassing the Sofnolime. If the bore is scratched, the O ring damaged or not lubricated or not replaced after a service, then CO2 will be inhaled!"
Within the last month on another Forum there were users keeping the O ring dry and pointing to instructors stating this is a good idea.
Sometimes I despair.
I suppose as it was media diving it came under the view of the HSE. And yeah I agree if someone stops and thinks then it's a good thing.
I agree with TheMac, I've never heard of anyone ever being told this, I've never met anyone who does it and no manufacturer recommends it. Depending on which bit of gossip you believe :D the instructor involved was investigated and struck off, if that's true then quite rightly so. Personally I'd like to see him prosecuted for such irresponsible behaviour but there you go.
Like TheMac also says, there is no way of predicting how much life is left in the lime. The reaction generates heat and there's a warm line which moves through the stack as the lime is used, at least one unit has a thermistor array to track the front's progress. How beneficial that is I don't know. When I was at Cranfield Uni they were doing research into it and found some bizarre temperature spikes happening as the lime was getting used up. There have been prototype CO2 sensors promised but there's nothing realistic available as yet. The real downside is that it doesn't take much CO2 to cause problems so I'm a bit sceptical as to how much use a sensor is.
I've had three CO2 problems and all three times it has been due to getting water in the stack. Most of the other incidents from people I know have been user error too. It's pretty hard for a properly assembled rebreather's scrubber to fail.
There is another situation where you can overbreathe the unit, if your breathing rate exceeds the speed at which the unit can remove CO2, the only way round that is to avoid exerting yourself. If you're trying to get down a shot in a running tide this is easier said than done. In situations like that I have gone to my open circuit bailout in the past.
The only real thing you can do to prevent it is to be very aware of your breathing rate and if it creeps up without any cause e.g. you aren't fighting a tide, then you have a problem. Again easier said than done. In one of the CO2 incidents I've had the simple act of changing from one mouthpiece to another was a massively stressful experience.
Cheers,
Stuart
Lizardland
29-11-07, 11:45
Other ways to get a CO2 hit. Inspiration specific.
1) Use the counter lungs as a BC. (easy to do and creates loads of other problems).
2) Do not fit the Scrubber O ring.
3) Do not grease the Scrubber O ring. Common sense?
The scrubber o-rings on the KISS are all captured o-rings and don't come out unless you've completely stripped it, I like that design but then the downside is that you get complacent and assume that it's there. However I grease them every time I open the scrubber which confirms they are still in place. I also like having smaller lungs which you can't use as a BC.
On the CK specifically:
- over or underpacking the scrubber (it's a fine line)
- overbreathing the scrubber by exertion, most of the CO2 incidents I've heard of on the CK have been down to divers working too hard
Within the last month on another Forum there were users keeping the O ring dry and pointing to instructors stating this is a good idea.
Sometimes I despair.
I've lost count of the number of times I've warned against that. I can't believe an instructor is teaching not to lube o-rings, it's basic stuff, rubber goes manky if you don't maintain it. Any time an o-ring on my RB sees light of day it gets inspected and a wipe of grease. First thing I did when I bought it (2nd hand) was take it apart, check the o-rings, replace the old ones and re-grease them all.