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. In addition to pure propane (propane content of 96% or more), propane-butane mixtures in various proportions are present on the market (sometimes gas companies simply call them propane, masking the real composition). These two gases (propane and butane) differ in their boiling points, at which they pass from a liquid to a gaseous state. Propane ceases to pass into gas and remains in a liquid state at a temperature of -43 °C, for butane this temperature is 0 °C. Therefore, the use of propane-butane mixtures has a temperature limit.