Denayrouze was born on October 1, 1837, at Montpeyroux, Aveyron, France, on the Aubrac plateau. In 1852, at the age of fifteen, he was admitted to the Naval School. He was promoted to lieutenant de vaisseau in 1862, and embarked on an expedition to Cochinchina (present-day Vietnam). He contracted a serious illness which rendered him unfit for service at sea. While recovering in the commune of Espalion, Denayrouze met Benoît Rouquayrol, with whom he took part in several inventions.
Since 1860, Rouquayrol had disclosed three patents for machines designed for mining emergencies, intended to furnish miners with air in case of firedamp or flooding of the mine. Denayrouze investigated the possibility of adapting the pressure regulator and developing it for underwater use. The two men thus designed and patented their "Rouquayrol-Denayrouze diving suit" in 1864. This would be the first diving suit that could supply air to the diver on demand. In the same year, the Imperial French Navy created a similar device.
In February 1865, August Denayrouze created the "Rouquayrol-Denayrouze Society" to commercialize their inventions for sale to both the Navy and to private enterprises. The same year, he created the "French Society for Fish and Sponges Of The Eastern Mediterranean," based in Izmir, Turkey. Two years later, the Rouquayrol-Denayrouze diving apparatus was presented at the 1867 World's Fair and won the gold medal.
Denayrouze died on 1 January 1883, aged 45, of illness.
Benoît Rouquayrol was born on June 13, 1826, at Espalion, in the Aveyron department of Southern France. He became an engineer at the Saint-Étienne School of Mines. He became employed at a company involved in bituminous coal mining and foundries in Aveyron, and became the director of accounting by 1865.
Rouquayrol’s Demand Regulator. The first and highly necessary component ofan open-circuit apparatus was a demand regulator. Designed early in 1866 and patented by Benoist Rouquayrol, the regulator adjusted the flow of air from the tank to meet the diver’s breathing and pressure requirements. However, because cylinders strong enough to contain air at high pressure could not be built at the time, Rouquayrol adapted his regulator to surface-supplied diving equipment and the technology turned toward closed-circuit designs. The application of Rouquayrol’s concept of a demand regulator to a successful open-circuit SCUBAwas to wait more than 60 years.
US Navy Diving Manual