Propane (the chemical formula C3H8) is an organic substance in the alkane class. Contained in natural gas, formed during cracking of petroleum products, in the separation of associated petroleum gas, as a by-product in various chemical reactions. Flammable and explosive, slightly toxic, has a specific characteristic odour and weak narcotic properties. A special odorant is added to the propane tank to detect leaks and prevent accidents. Propane has a much better calorific value than ethane and methane. Flammable propane easily reaches a combustion temperature of 1980 °C; therefore, it is often used in industry for gas cutting of metal, as well as in welding non-compliant structures.