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Its interesting this discussion has surfaced about using rebreathers for cave
diving.  I recall at the last National Speleological Society - Cave Diving
Section 
(NSS-CDS) conference we had Hal Watts and Ed Betts pushing rebreathers
in their talks.  When Hal was finished and opened the floor for questions I 
asked what I think was the obvious, "considering the safety rules in cave
diving such as the third's air rule and air sharing requirements, how does a
cave diver accomplish this without a redundant rebreather FOR CAVE
DIVING?" Kind of got a blank look and no relevant response. 'Sort of missing
the point if you have to carry stage bottles or diluent bottles with sufficient 
capacity to provide the reserve for reasonable dives.

Ed Betts was stating the Oceanic system has (would have) a shutdown time 
limit depending on how much training, and which system you bought (upgrade 
now for only $2000 !!!). That would certainly bite assuming you screwed up in
a cave and got lost and  now the rebreather starts telling you "shutdown in 5
minutes, sorry you don't have the upgrade!!!!" Never got a straight answer! 

I realize there are very special circumstances where a rebreather could be a 
valuable tool for specific applications in cave diving and could be used with
relative safety by highly experienced individuals.  However I would be
surprised 
to see an effective implementation of non-redundant systems that would satisfy 
the intent of proven safety guidelines for cave diving without losing the
benefits
of the system, without a greater system complexity. And we all know what that
means.

My greatest objection to the whole issue is these systems are being pushed off
on the various communities without having answers to the important questions. 
We know how they work, I've even used one, and could build one if need be,
but we need the operational end of the equation.  Until the vendors can answer
the questions, lets get speakers in conferences with topics more relevant to
the 
obvious.  Now openwater is a different beast!

Open to suggestions, 
Doug Chapman

P.S. This post is not meant to slam Hal and Ed, so don't get bent out of shape.

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