Ethylene (IUPAC name: ethene) is a hydrocarbon with the formula C2H4 or H2C=CH2. It is a colorless flammable gas with a faint "sweet and musky" odor when pure. An example of a niche use is as an anesthetic agent (in an 85% ethylene/15% oxygen ratio). It can also be used to hasten fruit ripening, as well as a welding gas.