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> Deformed canister didn't seem to catch your attention? Does the Cis 
> Lunar canister deform under pressure?

No.

> Since canisters are on our backs, it is hard to say if they deform, 
> but I don't think mine does! At least I don't have any leakage. I have 
> never seen a Drager unit, but from this post I would think it is very 
> frail?

I dunno, but I do know that the engineers at Draeger are not stupid, and 
I do know that they did one HELL of a lot of testing on those things.  If 
they drew a fill-line, I have a strong hunch that they had a reason to 
draw it wherever they did.  I know almost nothing about the Atlantis, so 
I very-well may be wrong.  However, I do know that one of the complex 
subtlties of rebreather operation is packing the canister correctly - and 
one of the most important things is to make sure that the absorbent won't 
settle (like a bag of potato chips) during the course of a dive and allow 
channeling.

> Channeling is the the obvious danger. With a good channel set up you 
> should have very little breathing resistance and extremely poor CO2 
> absorption outside of the channel. Nor should  there be much if any 
> noticeable breathing resistance if you have a good channeling system 
> set up. > 

I'm not sure I follow.  I got the first sentence, but I think I missed 
something on the second sentence.  My gut feeling is that we are in total 
agreement here.

> Death would be the big worry.

It usually is one of the bigger ones ;-)

> I would think these problems concern both semi-closed and fully-closed 
systems. > 

I think they are important to both types, but I think they are more 
important to fully-closed systems because you're not venting 25-30% of 
the CO2 in each breath (not that you're necessarily venting that much on 
a semi-closed, but it seems that the smart place to put the dump valve on 
these units in on the exhale side).

Rich

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