Acetylene (C2H2) is a hydrocarbon and the simplest alkyne. It has a broad application as a fuel and a chemical building block. One of its popular uses is in oxyacetylene gas welding and cutting due to the high temperature of the flame. In combination with oxygen, it produces the third-hottest natural chemical flame of over 6,020 °F, releasing 11.8 kJ/g. The acetylene torch is preferred for some sorts of iron or steel welding, but also because it can easily be used for brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), the loosening of corroded nuts and bolts, and other applications. Oxyacetylene welding may also be used in areas where electricity is not readily accessible.
Special care must be taken, for use in welding and cutting, by keeping the working pressure under 15 psi via the use of a regulator as above that acetylene can decompose explosively.