On receiving an actuation signal from a controller in response to an explosion or spark, the Valve is actuated by an electromagnetic solenoid valve. This fills a piston cylinder from its own air reservoir, forcing the gate to the closed position. The valve can be reopened manually by filling the opposite side of the piston cylinder or automatically by the press of a button, using another solenoid valve. Includes a shock absorber which reduces wear and tear. Air reservoir is filled by 6bar factory air.