A chlorine-containing organic compound, formula CH₃CCl₃. It is used in industrial applications as a solvent and a degreasing agent. The production of this compound is now forbidden as a result of the Montreal Protocol. Because its sources to the atmosphere (anthropogenic activity) and its losses (mostly through reaction with the hydroxyl radical) are well understood, the atmospheric abundance of this compound has been used to infer the average hydroxyl concentration in the troposphere.