Gagnan

Gagnan is a French surname. The most notable bearer is Émile Gagnan, a French engineer who, together with Jacques-Yves Cousteau, co-invented the Aqua-Lung, the first practical open-circuit scuba regulator.

Working for Air Liquide in the early 1940s, Gagnan helped adapt a high-pressure gas regulator into a demand valve suitable for underwater breathing. Cousteau, an explorer and naval officer, and Gagnan refined the equipment to deliver air from a cylinder on demand as the diver inhaled. In 1943 they patented the device, and it was marketed as Aqua-Lung, a precursor of modern scuba gear.

The invention enabled safe breathing underwater at depth and significantly influenced the development of recreational and professional diving, underwater exploration, and marine science. Gagnan’s contribution was primarily technical, focusing on the regulator mechanism that reduces cylinder pressure and provides air on demand.