GAS DETECTOR

摘要

First and second gas judging sections (4a, 4b) take in the outputs from first and second sensors (1, 2) at a specified sampling period and deliver a gas detection signal when a first contamination signal, determined from the difference between the outputs and a first reference level and indicating the degree of contamination of air, exceeds a specified detection level. A switching control section (5) receives the gas detection signal and switches a damper (20) to inner air circulation. Every time when a first update period longer than a sampling period elapses, a reference level updating section (6) multiplies the difference between the current output from each sensor (1, 2) and the first reference level used in previous update by a specified update ratio. The value added with the first reference level used in previous update is employed as a new first reference level thus increasing the speed for updating the first reference level in the clean direction as compared with a case where the first reference level is updated in the dirty direction.