Abstract: The invention relates to a gas chromatograph having a temperature-controlled injector for containing a vaporizer tube with chemical substances, thereon to be analyzed via a gas chromatography column, which temperature-controlled injector and vaporization tube can be heated by an electric resistance coil type of heating unit and can be cooled by a cooling unit, wherein the cooling unit has a cooling coil (7) which surrounds the heating unit and which is provided via a feedline and a return line (8, 9) with an external source of liquid, cooled coolant, with provision of a pump (11) for circulating the coolant and of a drain valve for draining the cooling coil.