Davis Submerged Escape Apparatus

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The Davis Submerged Escape Apparatus (also referred to as DSEA), is an early make of oxygen rebreather invented in 1910 by Sir Robert Davis, head of Messrs. Siebe Gorman and Co., inspired by the earlier Fleuss system. While intended primarily as an emergency escape apparatus for use by Royal Navy submarine crews, it was sometimes used for diving and as an industrial breathing set.

The DSEA rig comprises a rubber breathing/buoyancy bag, which contains a canister of barium hydroxide to scrub exhaled CO₂ and, in a pocket at the lower end of the bag, a steel pressure cylinder holding approx. 56 litres of oxygen at a pressure of 120 bar. The cylinder is equipped with a control valve and is connected to the breathing bag. Opening the cylinder's valve admits oxygen to the bag and charges it to a pressure equivalent to that of the surrounding water.

The canister of CO₂ absorbent inside the breathing bag is connected to a mouthpiece by a flexible corrugated tube; breathing is carried out by the mouth only, the nose being closed by a clip. Goggles are also provided as a standard part of the apparatus.

The breathing/buoyancy bag is fitted with a non-return release valve which allows air to escape from the bag as the user ascends towards the surface and the water pressure decreases. The wearer can close this valve on reaching the surface, the air in the breathing/buoyancy bag then serving as a life preserver. If the bag becomes deflated while the wearer is on the surface awaiting rescue, it can be refilled (for use as a lifejacket) by opening the non-return valve and blowing through the mouthpiece.

The typical RN DSEA rig also included an emergency buoyancy bag on the front of the main breathing/buoyancy bag, its purpose to assist the wearer to keep afloat after reaching the surface even if he had exhausted the air in the breathing/buoyancy bag. This emergency bag was inflated by means of an "Oxylet" canister inside it - a small steel oxygen cylinder which was opened by breaking its weakened neck and wrenching sharply.

It had a speed-retarding vane, which was a rubber apron, which was intended to be unrolled and held out horizontally by the wearer as he ascended, to control the speed of his ascent through water resistance.

The DSEA was used in the only known escape from a sunken submarine, HMS Perseus, which sank in 1941.

A small version of the DSEA, the Amphibious Tank Escape Apparatus (ATEA) was produced for use by the crews of amphibious tanks such as those used during the Normandy landings.