GAS SHUTOFF APPARATUS AND GAS SHUTOFF METHOD

A use condition of gas equipment is monitored. An abnormality determination unit 26 determines whether or not a use flow volume obtained by detecting a flow velocity obtained by measuring a signal transfer time in a medium using a flow velocity detection unit 17 and converting the detected flow velocity into a flow volume using a flow volume calculation unit 25. When the shutoff unit 27 shuts off a fluid path 1 when it is determined that there is abnormality, a return signal is output from a return unit 28 to a shutoff unit 27 in order to use the gas again by opening the fluid path. Simultaneously, when a return time-counting unit 29 starts the time-counting operation, and then, a predetermined time period has been elapsed, the flow volume calculation unit 25 determines whether or not a predetermined flow volume of greater flows in order to identify whether or not all of the gas plugs of the gas equipment connected to the downstream of the gas shutoff apparatus 27 are closed. The leakage determination unit 30 determines that there is leakage when a predetermined flow volume or greater is detected, and a driving signal is output to the shutoff unit 27 to close the fluid path 1.