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Today I went to a big diving exhibition at Excel in the Docklands in London (UK). In the rebreather exhibit I was told that in shallow diving the standard sport Inspiration's cylinders can last for 10 hours, but the absorbent canister for only 4 hours. He admitted that the canister may not be the best design for long duration. They said that the (UK) navy routinely uses sodium hydroxide as rebreather absorbent and puts up with the resulting risk of "getting a cocktail". Does sodium hydroxide give more duration than soda-lime or Sofnolime etc for the same volume? Otherwise, I wonder if sport rebreathers' absorbent canisters are purposely not designed to maximum duration so that they can't be used by unofficial bodies for long- duration "frogman-type" covert penetration and suchlike. I have heard of a new naval version of the Inspiration which has a black casing, no magnetic parts, all flexible parts reinforced with kevlar, and no consoles trailing on long hoses but instead a heads-up display in a fullface mask like some modern jet fighter helmets have. http://www.kuroyumes-developmentzone.com/appleyard/seapatrol/uw/sp2_salvus_attac k5.jpg Many rebreathers seem to give much less hydrodynamic drag in swimming and much less drag and inertia in rolling over than ordinary air scuba. I mentioned possible usefulness of this in by naval divers and diving sea-police giving better speed and agility underwater in arresting sport divers who get in the wrong place. He said that if the patrol diver has an Inspiration, in a fight with a suspect there is a risk of the suspect knowing about Inspirations and jabbing at the large and easily reached feed- pure-oxygen button, not a good thing at 60 feet. He said that in the naval version that vulnerability is corrected. The design of the Inspiratrion with the breathing bag in halves in front means that the breathing tubes are tehered to the shoulder straps part way along. That seems to be an advantage: there is no long trailing loop of tube behind where the frogman can't see it where it can catch on things or a suspect being arrested can attach it; and it seems to still allow full mobility of the head. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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