| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fire alarm that can prevent a fire alarm from being issued when there is no fire, while issuing the fire alarm immediately in the event of fire. <P>SOLUTION: The fire alarm comprises: a smoke detection unit 3 for detecting smoke; an alarm unit 4 for issuing the fire alarm; and a control unit 2 in which an accumulation time starts to be measured after the time when smoke density based on an output detected by the smoke detection unit 3 reaches a prescribed threshold or larger, and the alarm unit 4 issues the fire alarm when the smoke density continues to be equal to the threshold or larger for a prescribed time. The prescribed time is preliminarily set before the smoke density reaches the threshold or larger. The control unit 2, after the time when at least the smoke density reaches the threshold or larger, discriminates between fire and non-fire on the basis of a frequency spectrum in the amount of change of the smoke density during a prescribed analysis time, before the accumulation time reaches the prescribed time, and performs control either by reducing the prescribed time in the case of fire identification or by prolonging the prescribed time in the case of non-fire identification. <P>COPYRIGHT: (C)2012,JPO&INPIT |
