Coal mine rescue. 19th-century artwork of a coal mine rescue worker using breathing apparatus as he rescues a miner. This breathing apparatus was developed around 1865 by the mining engineer Benoit Rouquayrol. It was the first system that delivered air at the right pressure and on demand, which it did by using a valve system called a regulator. Air was breathed through the mouth from a pressurized supply on the rescue worker's back, and the nose was closed with a clip. Explosions caused by methane gas were one of the many dangers faced by 19th-century coal miners, along with the carbon dioxide produced from the burning methane. Engraving by P. Ferat and Hildibrand, published in Mines and Miners (L. Simonin, 1868).