putting 6 pounds of diver's weights (e.g. a pair of lead-shot-filled anklets) inside the wetsuit chest. The Salvus has no provision to connect to a buoyancy device; but the Salvus can be worn with a separate diver's lifejacket (not a stab jacket) which has its own small inflation cylinder. There is a small water catchment sump and drain on the underside of the canister. Its cylinder pressure gauge is on a flexible metal tube and fits in a circular webbing pouch threaded on the waist harness strap. The bag tube unscrews from the canister pack. The diagonal strap clips onto a corner of the side-pack. The cylinder has a constant-flow valve and a bypass. The thread on top of the cylinder is the same as on an oxy-gas torch oxygen cylinder but the opposite gender, for easy refilling by decanting. History Early versions were originally designed for use in bad breathing conditions such as in underground mines and other enclosed spaces, where heavy concentrations of noxious gases could build up and affect the workers. During World War I, Salvuses were used by machine gunner units on the Western Front (1915) as an interim protection against enemy gas weapons. During World War II the Salvus Mk.VI model was used by British troops. Mk. VI's were also used by the National Fire Service: their cooler boxes were marked with the letters 'NFS'. War-surplus Salvuses were much used by early sport divers in Britain and Australia in the 1950s before aqualungs became readily affordably available. At the coalmine rescue on 7–9 September 1950 at Knockshinnoch Castle Colliery near New Cumnock, Ayrshire, Scotland, 115 trapped miners were equipped with Salvuses borrowed from fire stations around to bring them out through a gas-filled mine passage. References External links DG8FZ.dyndsn.org: Karl's Kreislauftauchgeräte Seite Salvus Rebreather http://www.therebreathersite.nl/Zuurstofrebreathers/English/salvus.htm description Rebreathers Industrial breathing sets