Siebe Gorman Proto
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The Proto is a type of rebreather that was made by Siebe Gorman. It was an industrial breathing set and not suitable for diving. It was made from probably 1914 or earlier to the 1960's or later. (Distinguish from "Proton", which is another sort of Siebe Gorman rebreather).
Its breathing bag was worn on the chest. It had one or two oxygen cylinders, across the lumbar part of the back. Its duration in use was one to two hours. Its absorbent was loose in the bottom of the breathing bag, restrained by a perforated cloth partition, and not in a canister. It had two wide breathing tubes running from the breathing bag to either a strapped-in mouthpiece (used with goggles) or an industrial-type fullface mask with a curved window and an inner ori-nasal mask. The canister seen on the front of the bag was to cool the gas in circuit, as the absorbent gets warm as it absorbs carbon dioxide, and that warming of the gas in circuit is welcome when scuba diving in cold water, but is not welcome in hot industrial situations including in deep mines.
It was much used by firefighters and in rescue in coalmines, long before open-circuit industrial breathing sets based on the aqualung became common. It appeared in many news images of coalmine rescue squads.
