a shut - off device for use with an internal combustion engine having an electric ignition comprises a switch having first and second states , connected to the engine ignition in such a way that the ignition current is not inhibited when the switch is in its first state but is inhibited when the switch is in its second state . the device further has means for changing the switch from its first state to its second state and means for automatically maintaining the switch in its second state for a predetermined interval of time sufficient to allow the engine to die .