Abstract: A gas supply pipe is provided with a terminal shutoff valve upstream of a heater, stove or the like. An automatic shutoff valve is provided to the gas pipe upstream of the terminal shutoff valve which automatically closes upon receipt of an electrical signal from an earthquake sensor, fire detector, gas leak detector or other sensor indicating a dangerous condition. A gas pressure sensor provided between the automatic shutoff valve and the terminal shutoff valve prevents the automatic shutoff valve from being manually reset unless the terminal shutoff valve is closed, thereby preventing an explosion which might result if gas were fed to the heater or stove with the pilot light extinguished.