| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas detection apparatus for reliably and readily detecting the increase in gas concentration by using simple processing, to provide a gas detection apparatus having fewer wrong determinations, and to provide an auto ventilation system for vehicles which uses the gas detection apparatus. SOLUTION: The gas detection apparatus for using a gas sensor element 11, where sensor resistance Rs changes according to gas concentration acquires a sensor output value S from a sensor resistance conversion circuit 14, calculates a base value B(n) according to B(n)=B(n-1)+k1 S(n)-B(n-1)} and B(n)=S(n) when S(n)>=S(n-1) and S(n)<S(n-1), respectively, and further calculates a difference value D(n)=S(n)-B(n). When the gas concentration increases and the difference value becomes larger than a specific concentration threshold, a concentration high signal is generated and a flap 34 is closed, a coefficient k2 that is smaller than k1 is used, and the base value B(n) is calculated.
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