page_title: Siebe Gorman CDBA
section_title: Design
hierarchical_section_title: Siebe Gorman CDBA / Design
caption_attribution_description: English: 2 types of British frogmen's and naval divers' rebreather fullface masks: older (e.g. WWII) type with the oval window, newer with the rectangular window mostly flat but folded back at the sides.
context_page_description: The Clearance Divers Breathing Apparatus is a type of rebreather made by Siebe Gorman in England.
  The British Royal Navy used it for many years. It was for underwater work rather than for combat diving. The main oxygen cylinders are on the diver's back. The oxygen cylinders at the front of the diver are for bailout. In its basic mode it was an oxygen rebreather; but some of the cylinders could be replaced by diluent cylinders for nitrox mode, and then the set was sometimes called CDMBA. The Royal Navy was using nitrox from 1944, but did not reveal its nitrox techniques, and in the 1960s and afterwards civilian divers had to retread the same ground and develop nitrox diving independently. In later years it was called DSSCCD from "Diving Set, Self-Contained, Clearance Diver".
context_section_description: The CDBA was very popular with the clearance divers. It is comfortable since there is no cylinder on the middle of the back, no bulky buoyancy compensator, and it requires very little weight.
  As the rebreather has a single "pendulum" breathing tube, the diver must breathe deeply to avoid carbon dioxide build-up. The counterlung is eight litres. As with all rebreathers, the diver should breathe continuously to keep the gas flowing over the absorbent. Dives on the unit are limited to 90 minutes.
  Instead of a weight belt there is a weight pouch at the back, full of lead ball weights 38 mm (1.5 in) in diameter. In an emergency, the diver could pull a line which opened the weight pouch to jettison these weights.
  It is intended to be used with a fullface mask with one breathing tube. At first (during World War II and after) a mask with an oval or circular flat window (as seen in images at this link) was used; later the mask with the newer type of rectangular window mostly flat but folded back at the sides was used.
caption: 2 types of fullface mask used with the CDBA and UBA and SCBA; the oval type is older.
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