Escape set

An escape set (in German Tauchretter = "diver rescuer") is a breathing set, which lets its wearer survive for a time in an environment without (sufficiently) breathable air, in particular underwater, primarily or originally intending mainly to survive long enough to reach safety where the air is breathable.

Early escape sets were rebreathers and were used to escape from a submarine which was submerged so long that its onboard air supply ran out, and for technical or military reasons the submarine could not surface: one example is the Davis Submerged Escape Apparatus. Escape sets were also used ashore, e.g. in the mining industry.

Currently, language in German as in English, tauchen = "diving" only means in water. Until the middle of the 20th century the German word tauchen = "to dive" also meant "to stay in unbreathable atmosphere". Thus around 1900 a water-cooled fire protection hood with air supply for firefighters was called in German a Feuertaucher (= "fire diver"), and still into the 1940s in German a man with a breathing apparatus for use in unbreathable atmosphere was called a Gastaucher (= "gas diver"). But as escape sets were used more for rescue from sunken submarines and as light diving equipment, the German word "tauchen" was restricted to underwater meanings.

Normal breathing air contains about 20% oxygen. In normal breathing the body uses about 4% and replaces it with carbon dioxide. A certain volume of air can be "breathed deeply" several times, until its oxygen portion is exhausted. However, each breath becomes heavier, since carbon dioxide accumulates and oxygen is used up. Therefore, this accumulating carbon dioxide must be removed from the breathing cycle.

For the general function of this sort of breathing set, see rebreather.

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