| 摘要 |
<P>PROBLEM TO BE SOLVED: To automatically detect and report abnormality, such as dirt or breakage of an insect proof cover for housing a detection part in a smoke type fire alarm. Ž<P>SOLUTION: In the smoke type fire alarm 1 for housing smoke sensors 11a, 11b inside the insect proof cover 19, an air hole 19a is formed on the insect proof cover 19, first and second electrodes 20a, 20b are included on an insect proof wall 19b comprising insulators, and a measurement part 17a for applying a voltage for measurement between the first and the second electrodes 20a and 20b to measure a capacity and a control unit 18 for operating the measurement part 17a by a prescribed cycle and outputting abnormality alarm when the measured capacity is changed from a reference value for a prescribed amount are included. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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