Abstract: The described invention takes as its basis the problem of developing an overtemperature shut-off valve which guarantees a reproducible gas-tight seal. The problem is solved in that the metal closure body (11) has a spherical shape at least in its sealing area and its diameter is selected so as to form a slight tight fit with the diameter of a valve seat which is in the form of a bore (21) shaped in the housing (1) of the valve when the valve is closed. A second bore (20) extends in the direction of the first bore (21) is arranged upstream thereof. A guide (19) that tapers outwardly in the direction of the closure body (11) when it is in its open position is located between the closure body and the second bore (20).