Patent ID: 8773272

Claim:
A light scattering type smoke sensor comprising: a sensor body; a light-emitter that is incorporated in the sensor body to emit light toward an open smoke-sensing space located outside the sensor body; a light-receiver that is incorporated in the sensor body to receive scattered light generated by the light emitted from the light-emitter to the smoke-sensing space, and to output a light-received signal corresponding to an amount of received light scattered; and a fire judging unit that judges presence/absence of fire occurrence based on the amount of received light identified by the light-received signal output from the light-receiver, wherein the fire judging unit judges that fire occurs, when the amount of received light exceeds a predetermined first fire threshold for a time equal to or longer than a predetermined first set time, and the amount of received light exceeds a predetermined second fire threshold which is higher than the first fire threshold for a time equal to or longer than a predetermined second set time.