| 摘要 |
PROBLEM TO BE SOLVED: To reduce delay in detection with respect to sudden generation of combustible gas of high concentration. SOLUTION: A metal oxide semiconductor gas sensor 2 is alternately heated to a high-temperature region and a low-temperature region, and the combustible gas is detected in the high-temperature region and CO is detected in the low- temperature region. The output of the gas sensor at the end of the high- temperature gegion is increased or is almost constant, and when it is estimated that the gas is present from the output of the gas sensor, the high-temperature region is extended. The output of the gas sensor is sampled at a high frequency when extending, and the concentration of the combustible gas not less than an alarm level is detected or the extention is released, after the elapse of a prescribed time and the temperature of the gas sensor is changed to the low- temperature region.
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