Aqua-Lung

Aqua-Lung^[1] was the first open-circuit, self-contained underwater breathing apparatus (or "scuba") to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin-hose diving regulator,^[2] or demand valve. The Aqua-Lung was invented in France during the winter of 1942–1943 by two Frenchmen: engineer Émile Gagnan and Jacques Cousteau, who was a Naval Lieutenant (French: lieutenant de vaisseau). It allowed Cousteau and Gagnan to film and explore underwater more easily.^[3]

The invention revolutionised autonomous underwater diving by providing a compact, reliable system capable of a greater depth range and endurance than its precursors, and was a major factor influencing the development of recreational scuba diving after WWII.

The twin-hose Aqua-Lung demand regulator is the foundation of all modern scuba regulators. A diaphragm is used to control a valve to deliver the breathing gas to the diver on demand, at ambient water pressure. However, the layout has changed to a single hose system, where the second stage is split from the first stage along with the exhaust valve, as they must be kept at the same depth, and repositioned at the diver's mouth, eliminating the need for the exhaust hose, and allowing the use of a more rugged, smaller bore hose for the intermediate pressure gas supply to the second stage valve at the mouthpiece, but increasing the load on the diver's jaw and releasing bubbles nearer the eyes and ears.

^ After Cousteau himself, who had coined the word, the spelling was originally Aqua-Lung. See Jacques-Yves Cousteau & Frédéric Dumas, Le Monde du silence, Éditions de Paris, Paris, 1953, Dépôt légal 1er Trimestre 1954 - Édition N° 228 – Impression N° 741 (in French)
^ Both regulators—the one from 1860 invented by Benoît Rouquayrol and the twin-hose Cousteau-type invented in 1943 by Gagnan and Cousteau—received, among some others, the name of régulateur (French for "regulator"). For the 1860 régulateur see the page of the Rouquayrol-Denayrouze apparatus in the Musée du Scaphandre website (a diving museum in Espalion, south of France) Archived June 30, 2011, at the Wayback Machine. For the word régulateur as used by Cousteau himself just check page 8 in the first French edition of Cousteau's book The Silent World: Jacques-Yves Cousteau & Frédéric Dumas, Le Monde du silence, Éditions de Paris, Paris, 1953, Dépôt légal 1er Trimestre 1954 – Édition N° 228 – Impression N° 741 (in French).
^ Than, Ker (11 June 2010). "Jacques Cousteau Centennial: What He Did, Why He Matters". news.nationalgeographic.com. Archived from the original on June 14, 2010. Retrieved 3 March 2016.

[1] After Cousteau himself, who had coined the word, the spelling was originally Aqua-Lung. See Jacques-Yves Cousteau & Frédéric Dumas, Le Monde du silence, Éditions de Paris, Paris, 1953, Dépôt légal 1er Trimestre 1954 - Édition N° 228 – Impression N° 741 (in French)

[2] Both regulators—the one from 1860 invented by Benoît Rouquayrol and the twin-hose Cousteau-type invented in 1943 by Gagnan and Cousteau—received, among some others, the name of régulateur (French for "regulator"). For the 1860 régulateur see the page of the Rouquayrol-Denayrouze apparatus in the Musée du Scaphandre website (a diving museum in Espalion, south of France) Archived June 30, 2011, at the Wayback Machine. For the word régulateur as used by Cousteau himself just check page 8 in the first French edition of Cousteau's book The Silent World: Jacques-Yves Cousteau & Frédéric Dumas, Le Monde du silence, Éditions de Paris, Paris, 1953, Dépôt légal 1er Trimestre 1954 – Édition N° 228 – Impression N° 741 (in French).

[NatGeo_2010-3] Than, Ker (11 June 2010). "Jacques Cousteau Centennial: What He Did, Why He Matters". news.nationalgeographic.com. Archived from the original on June 14, 2010. Retrieved 3 March 2016.

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