This article is the result of a breathing device shown to me by a friend. He asked me if I could tell him what this unit was build for. Since nobody could tell me anything about the origin I decided to put it on my ULO page. It resulted in a reaction of Mr. Iain who explained me the unit. I am still looking for additional information, so if you have experience with this unit, please don't hesitate to contact me.

This was an excellent design also using many of the parts in the better known mixed gas/oxygen Clearance Divers Breathing Apparatus CDBA.

There were only two small changes to convert from DCBA to SDDE namely an aluminium back plate and a small adapter to connect a surface supplied umbilical. No longer in service with Royal Navy but some overseas navies still call spares.

At the time the Royal Navy already had a SCUBA variant called the SABA set Swimmers Air Breathing Apparatus and the closed circuit oxygen and semi closed 60/40, 40/60 32.5 mixed gas clearance divers set called the CDBA for diving to 55 MSW both of these units worked well from the Gemini inflatable boats. However the surface supplied SDDE was difficult to operate from the Gemini due to having to have storage bottles, a diver panel, and two umbilicals.

Also at the time a deep water mixed gas semi closed variant was used for secret operations called the Mark 4C. Designed primarily for SUBSMASH this unit was used from 1975. Some aspects of the Mark 4 project may still be classified, I will check on this but incidentally working at 100MSW semi closed in cold 4 deg C water the maximum measured 0₂ uptake was 2.7 L/min at 63 MSW resulting in a P02 of 0.42 bar. The deep diving version of this unit was rated to 350MSW.

Pics of DCBA / SDDE below if you need more info let me know.

Iain, thanks for contributing to my website!