An early self-contained oxygen rebreather that, in the early part of the 20th century, was originally intended for land-based use in underground mines and other confined spaces containing poisonous atmospheres (including being used during WWI to protect machine gunners serving in the trenches of the Western Front from gas attack) the ‘Salvus’ set – designed and manufactured by Siebe, Gorman & Co. – was, in 1942 during WWII, and with slight modifications, adapted for use by the Royal Navy in shallow-water diving operations similar to those previously undertaken by people like ‘Buster’ Crabb and the Underwater Working Party, in Gibraltar; divers who had previously relied on Davis Submarine Escape Apparatus for life-support.
Modified into a pendulum-breathing diving set for general use down to 33-feet by removing the relief valve and putting a plug into the canister, the ‘Salvus’ set was the fore-runner of the Clearance Divers Breathing Apparatus (CDBA) – an adaptable piece of kit that could be configured for O2 or Nitrox diving and that was in use through until the 1970’s when it was superseded by the Drager FGT.
Eagerly sought after by sports divers who, during the 1950’s, bought WWII surplus ‘Salvus’ units as being more affordable than the newly developed, ‘Aqualung’, the ‘Salvus’ apparatus – although no longer considered suitable for diving purposes – remained a key part of a ship’s fire-fighting capabilities through until recent times*.
* My “recent” refers to the 1960’s/’70’s. 😊