page_title: History of underwater diving
section_title: Closed-circuit scuba
hierarchical_section_title: History of underwater diving / Self-contained air supply equipment / Closed-circuit scuba
caption_attribution_description: English: Photo of Henry Albert Fleuss Русский: Флюсс, Генри Альберт
context_page_description: The history of underwater diving starts with freediving as a widespread means of hunting and gathering, both for food and other valuable resources such as pearls and coral, By classical Greek and Roman times commercial applications such as sponge diving and marine salvage were established, Military diving also has a long history, going back at least as far as the Peloponnesian War, with recreational and sporting applications being a recent development. Technological development in ambient pressure diving started with stone weights for fast descent. In the 16th and 17th centuries diving bells became functionally useful when a renewable supply of air could be provided to the diver at depth, and progressed to surface supplied diving helmets - in effect miniature diving bells covering the diver's head and supplied with compressed air by manually operated pumps - which were improved by attaching a waterproof suit to the helmet and in the early 19th century became the standard diving dress.
  Limitations in mobility of the surface supplied systems encouraged the development of both open circuit and closed circuit scuba in the 20th century, which allow the diver a much greater autonomy.
context_section_description: The alternative concept, developed in roughly the same time frame was closed-circuit scuba. The body consumes and metabolises only a part of the oxygen in the inhaled air at the surface, and an even smaller fraction when the breathing gas is compressed as it is in ambient pressure systems underwater. A rebreather recycles the used breathing gas, while constantly replenishing it from the supply so that the oxygen level does not get dangerously depleted. The apparatus also has to remove the exhaled carbon dioxide, as a buildup of CO₂ levels would result in respiratory distress due to hypercapnia.
  The earliest known oxygen rebreather was patented on 17 June 1808 by Sieur Touboulic from Brest, mechanic in Napoleon's Imperial Navy, but there is no evidence of any prototype having been manufactured. This early rebreather design worked with an oxygen reservoir, the oxygen being delivered progressively by the diver himself and circulating in a closed circuit through a sponge soaked in limewater. The earliest practical rebreather relates to the 1849 patent from the Frenchman Pierre Aimable De Saint Simon Sicard.
  The first commercially practical closed-circuit scuba was designed and built by the diving engineer Henry Fleuss in 1878, while working for Siebe Gorman in London. His apparatus consisted of a rubber mask connected by a tube to a bag, with (estimated) 50–60% O₂ supplied from a copper pressure tank and CO₂ chemically absorbed by rope yarn in the bag soaked in a solution of caustic potash. The system allowed use for about three hours. Fleuss tested his device in 1879 by spending an hour submerged in a water tank, then one week later by diving to a depth of 5.5 metres (18 ft) in open water, upon which occasion he was slightly injured when his assistants abruptly pulled him to the surface. The Fleuss apparatus was first used under operational conditions in 1880 by the lead diver on the Severn Tunnel construction project Alexander Lambert, who was able to travel 1,000 feet (300 m) in the darkness to close several submerged sluice doors in the tunnel; this had defeated the best efforts of hard hat divers due to the danger of their air supply hoses becoming fouled on submerged debris, and the strong water currents in the workings. Fleuss continually improved his apparatus, adding a demand regulator and tanks capable of holding greater amounts of oxygen at higher pressure.
  Sir Robert Davis, head of Siebe Gorman, improved the oxygen rebreather in 1910 with his invention of the Davis Submerged Escape Apparatus, the first rebreather to be made in quantity. While intended primarily as an emergency escape apparatus for submarine crews, it was soon also used for diving, being a handy shallow water diving apparatus with a thirty-minute endurance, and as an industrial breathing set. The Davis apparatus comprised a rubber breathing bag containing a canister of barium hydroxide to scrub exhaled carbon dioxide and a steel cylinder holding approximately 56 litres (2.0 cu ft) of oxygen at a pressure of 120 bars (1,700 psi), with a valve to allow the user to add oxygen to the bag.  The set also included an emergency buoyancy bag on the front of to help keep the wearer afloat. The DSEA was adopted by the Royal Navy after further development by Davis in 1927.
  The rig comprised a rubber breathing/buoyancy bag containing 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 approximately 56 litres (2.0 cu ft) of oxygen at a pressure of 120 bars (1,700 psi). The cylinder was equipped with a control valve and was connected to the breathing bag. Opening the cylinder's valve admitted oxygen to the bag at ambient pressure. The rig also included an emergency buoyancy bag on the front of to help keep the wearer afloat. The DSEA was adopted by the Royal Navy after further development by Davis in 1927.
  In 1912 the German firm Drägerwerk of Lübeck introduced their own version of standard diving dress using a gas supply from an injector-circulated oxygen rebreather and no surface s
caption: Henry Fleuss (1851-1932) improved the technology of the closed circuit oxygen rebreather .
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