Aqua-Lung

Aqua-Lung was the original English name of the first open-circuit, self-contained underwater breathing apparatus (or "SCUBA") to reach worldwide popularity and commercial success. This class of equipment is now commonly referred to as a diving regulator or demand valve. The Aqua-Lung was invented in Paris during the winter of 1942–1943 by two Frenchmen: the engineer Émile Gagnan and Naval Lieutenant ("lieutenant de vaisseau") Jacques Cousteau. It allowed Cousteau and Gagnan to film and explore more easily underwater.

An earlier underwater breathing regulator, known as the régulateur, was invented in France in 1860 by Benoît Rouquayrol. He first conceived it as a device to help assist in escaping from flooded mines. The Rouquayrol regulator was adapted to diving in 1864, when Rouquayrol met the lieutenant de vaisseau Auguste Denayrouze. The Rouquayrol-Denayrouze apparatus went into mass production and commercialization on 28 August 1865, when the French Navy Minister ordered the first apparatuses.

After 1884, several companies and entrepreneurs bought or inherited the patent and produced it until 1965. In 1942, during the German occupation of France, the patent was held by the Bernard Piel Company (Établissements Bernard Piel). One of their apparatuses went to Émile Gagnan, an engineer employed by the Air Liquide company. Gagnan miniaturized and adapted it to gas generators in response to a fuel shortage, which was a consequence of German requisitioning. Gagnan's boss, Henri Melchior, knew that his son-in-law Jacques-Yves Cousteau was looking for an automatic demand regulator to increase the useful period of the underwater breathing apparatus invented by Commander Yves le Prieur, so he introduced Cousteau to Gagnan in December 1942. On Cousteau's initiative, the Gagnan's regulator was adapted to diving, and the new Cousteau-Gagnan patent was registered some weeks later in 1943. After the war, in 1946, both men founded La Spirotechnique (as a division of Air Liquide) in order to mass-produce and sell their invention, this time under a new 1945 patent, and known as CG45 ("C" for Cousteau, "G" for Gagnan and "45" for 1945). This same CG45 regulator, produced for more than ten years and commercialized in France as of 1946, was the first to actually be called the "Aqua-Lung". In France, the terms scaphandre autonome ("scuba set"), scaphandre Cousteau-Gagnan ("Cousteau-Gagnan scuba set"), or CG45 were meaningful enough for commercialization, but to sell his invention in English-speaking countries, Cousteau needed an appealing name following English language standards. He then coined the trade name Aqua-Lung.

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