Rouquayrol quickly climbed the company's administrative ladder and became the director in 1865. During this period there were many mine collapses and disasters, often with fatalities. Rouquayrol took an active role in mine safety issues and paid particular interest to the problem of saving the lives of miners who were trapped in collapsed tunnels that were often filled with toxic gasses.
The miners' means of protection were very few and none of them could be used to evacuate the miners caught in the layers of gas without putting the rescuers from the surface in peril. The rescuers did not have a way to safely penetrate into the mines immediately after an incident. They often had to wait a long period of time for natural ventilation to clear the toxic gases, and by that time, it was often too late to resuscitate the victims. Aware of this tragic situation, Rouquayrol set about developing and constructing an apparatus which permitted rescuers to penetrate the mines while being able to breath normally. In his pursuit of this goal he first invented a demand regulator which was granted a patent on April 14,1860. It was this regulator, combined with his later inventions, and adapted with the assistance of Auguste Denayrouze, that would become a production diving unit that had the capabilities to be used as a self-contained underwater breathing unit SCUBA.
On the January 16,1862, Rouquayrol was granted a second patent for another apparatus called the Rouquayrol Isolation equipment, which was a low pressure reservoir. The demand regulator would attach to this reservoir making a single back pack unit. On August 25,1863, he received a third patent for a water cooled pump that supplied air to the reservoir and regulator backpack. The pump also featured a novel hydraulic sealing design which greatly improved its efficiency.
When the three patented items Rouquayrol had created were combined, they formed a pumped air supply to a reservoir, which held the compressed air, from which the wearer could breath by demand through the regulator mouth piece. The reservoir could also be pressurised by the pump, and then detached from it, allowing the wearer to have a self-contained air supply with which he could travel further than the restrictive length of the pump hose. Rouquayrol also made the first test dives with the system.
Auguste Denayrouze was bom on October 1,1837, in Giscard, in the community of Montpeyroux, France. He entered the French navy training program in 1851 and served in the Crimean war. His commanding officer wrote of him, "This young man is very gifted for a career in the navy. Very intelligent, very studious, thoughtful, steady, zealous, he learns with a wonderful easy facility. He serves admirably. He promises to be a distinguished officer."
On October 8,1862, he was promoted to Ships Lieutenant. His career was stifled in 1864 when he contracted a grave chest infection. He was declared unfit for service on the high seas, and was put on a three-year temporary leave. Denayrouze went to Espalion to recuperate, and there discovered the new inventions of Rouquayrol, whom he knew well as their families were related. Denayrouze was enthusiastic about his friend's apparatus as he could see how this equipment, that was designed for saving lives in the mines, could be adapted to Navy needs. Denayrouze moved to Paris, and there he actively helped in the manufacturing of the first breathing apparatus given by Rouquayrol to a Parisian Aveyronais artisan named Aygalenc. He also helped with ideas for certain modifications.
Denayrouze was soon in constant communication with Benoit Rouquayrol via mail, as they worked on the technical details of the breathing apparatus. With his navy connections he was able to get the new diving system onto a navy salvage job. The system worked well and Denayrouze committed himself to developing it. He took charge of the marketing, put up 10,000 Francs and also raised 20,000 Francs from an Espalion businessman, Camille Marcilhacy. With 30,000 Francs at their disposal, the newly funded partnership of Rouquayrol - Denayrouze, in collaboration with Marcilhacy, set out on a manufacturing and design path that would make diving history. After Benoit Rouquayrol passed away, Denayrouze operated the company under his own name, and the Denayrouze company went on to amass a financial fortune providing gas lights to illuminate French streets.