Oxyhydrogen

Oxyhydrogen is a mixture of hydrogen (H₂) and oxygen (O₂) gases. This gaseous mixture is used for torches for the processing of refractory materials and was the first gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is required to avoid an oxidizing flame.