| 摘要 |
PROBLEM TO BE SOLVED: To selectively and safely detect CO gas by disposing a filter absorbing NO, NO2 and SO2 and permitting carbon monoxide to pass to a passage for introducing gas to be detected into a detection element. SOLUTION: The surface of a detection element 1 is covered with a filter housing 12. An opening 13 is provided to the top part of the housing 12 and gas to be detected is introduced from the opening 13 to transmit through filters 7, 8 of a two-layered stucture while diffusing throughout them to arrive at the surface of the element 1. At this time, NO, NO2 and SO2 are adsorbed by activated carbon or reacted with alkali metal carbonate along with moisture contained in the gas to be detected to be reduced in the amt. arriving at the surface of the detection element 1. Contrarily, carbon monoxide is slight in the amt. adsorbed by activated carbon and not reacted with alkali metal carbonate. Therefore, the influence of NO, NO2, SO2 or the like on the detection element 1 is reduced and the detection sensitivity to carbon monoxide thereof is stabilized and carbon monoxide can be selectively detcted.
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