Abstract: An inertial trip valve actuated by vibration to close gas lines and the like in the event of earthquake for safety. Said valve is provided with an external reset. Said reset cannot be used to defeat the operation of the device by tying the reset handle because the reset action momentarily closes the valve. The valve comprises an inlet flapper valve and an outlet shear valve. Said flapper valve is closed under a spring load when an inertial trigger is tripped. Said flapper valve may be reset by an external handle which closes a shear valve during the reset operation thus preventing the defeat of the trigger operation.