| 摘要 |
PROBLEM TO BE SOLVED: To provide a detector enabling to grasp an amount of stain of a light receiving glass without providing a light emitting element for detecting stain on the fire detector. SOLUTION: In this fire detector in which a light receiving element facing a monitored zone is arranged inside a light receiving glass, an illumination light amount detecting means for detecting a light receiving amount by illumination light, and an amount detecting means for detecting an amount of stain of the light receiving glass based on change of the light receiving amount detected by the illumination light amount detecting means are provided.
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