Before 1945, French divers preferred the traditional copper helmet standard diving dress. The Rouquayrol-Denayrouze apparatus did not achieve as much success because the compressed-air tanks made with the technology of the time could only hold 30 atmospheres, which allowed dives of only 30 minutes at no more than ten meters deep. In the late 1940s and early 1950s, La Spirotechnique started exporting the Aqua-Lung and leasing its patent to foreign companies like the British Siebe Gorman.
In France, the terms scaphandre autonome ("autonomous diving set"), scaphandre Cousteau-Gagnan ("Cousteau-Gagnan diving 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. 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". 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). Cousteau and Gagnan were issued a patent some weeks later in 1943. On Cousteau's initiative, the Gagnan regulator was modified for use in diving. 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 endurance of the underwater breathing apparatus invented by Commander Yves le Prieur, so he introduced Cousteau to Gagnan in December 1942. Gagnan miniaturized and adapted it to gas generators in response to a fuel shortage, which was a consequence of German requisitioning. One of their apparatuses went to Émile Gagnan, an engineer employed by the Air Liquide company. In 1942, during the German occupation of France, the patent was held by the Bernard Piel Company ( Établissements Bernard Piel). Īfter 1884, several companies and entrepreneurs bought or inherited the patent and produced it until 1965. The Rouquayrol-Denayrouze apparatus went into mass production and commercialization on 28 August 1865, when the French Navy Minister ordered the first units. The Rouquayrol regulator was adapted to diving in 1864, when Rouquayrol met the lieutenant de vaisseau Auguste Denayrouze. He first conceived it as a device to help assist in escaping from flooded mines. An earlier underwater breathing regulator, known as the régulateur, was invented in France in 1860 by Benoît Rouquayrol.