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摘要

P To shut OFF a gas for a safe duration time at a proper timing by improving a method of determining the presence or absence of flow variation by determining the presence or absence of actual flow variation in a normal operation or a non-use state in such a state that the gas is left in a turned-on state. PSOLUTION: A flow variation determination processing for preventing early shutoff, a flow variation determination processing for preventing late shutoff and a reducing-direction flow variation determination processing are performed in parallel by a flow variation detecting section 112, a counting section 113, a flow variation presence/absence determining section 114 and a security section 116. In the flow variation determination processing for preventing early shutoff and the determination is performed under a determination condition that flow variations of a flow variation minimum value or more occur by a prescribed number of times (N times) or more. In the flow variation determination processing for preventing late shutoff and the determination is performed under a determination condition that flow variation of an ignition flow rate minimum value or more occurs. In the reducing-direction flow variation determination processing and the determination is performed under a determination condition that flow variations of a reducing-direction variation determination value or more occur by a prescribed number of times (M times) or more within a prescribed time (X hours). PCOPYRIGHT: (C)2010 and JPO& INPIT