Why so many deaths on CCR?

[Dsix36]

Can someone summarize how people typically die on rebreathers?

My impressions are as follows, but I do not know if I am correct.

0. CO2 issues related to maintenance of the scrubber get you.
1. The operator fails to keep his PPO2 correct (manual unit)
2. Bad sensors give the operator or magical mixing computer false information about PPO2
3. Way down the list would be other mechanical failures not related to gas mixing, eg floods, which are not properly handled

In rebreather deaths, is it more common for the unit to fail you, and knock you out or make you tox... or is it more common for the user to make errors?

It is going to be almost impossible to get an honest and straight answer to your question. With most rebreather fatalities, the exact case of death is never known. There is always a lot of speculation and debate as to the cause, but very seldom is there any concrete evidence.

I look at it a bit different than a lot of others. I believe that every death that occurs to a diver while using a rebreather is due to user error. There is of course the exceptions for things that would have the same outcome if diving with open circuit gear (shark attack, brain anursym, heart attack, etc).

We are trained to deal with every possible failure mode and should always keep our skills sharp. Compacency kills and diligence is required. Anything else is stupid and Darwin is right around the corner.

If there is no way to keep the rebreather operating in a safe manner, we will bailout to open circuit and end the dive.

CO2 is the only thing that we have to rely upon faith to maintain. Faith in our gear preparation and faith that we are not stretching our CO2 absprbent time. Other than that, PO2 should be monitored religiously. Failure to do so may end in death.