Patent ID: 8409414

Claim:
A gas sensor for measuring an amount of a to-be-measured gas component in a to-be-measured gas present in an external space, which comprises: a solid electrolyte which is in contact with an external space, an internal space formed inside the solid electrolyte, a first diffusion resistance portion and a second diffusion resistance portion for introducing the to-be-measured gas from the external space via a gas inlet, at a given diffusion resistance, a pumping means which has an inner pumping electrode formed inside the internal space and an outer pumping electrode formed outside the internal space and which subjects the oxygen contained in the to-be-measured gas introduced from the external space, to a pumping treatment based on a controlling voltage applied between the two electrodes, a gas component-measuring means having a detection electrode, which electrode decomposes the to-be-measured gas component contained in the to-be-measured gas after the pumping treatment by the pumping means and measures the to-be-measured gas component contained in the to-be-measured gas, based on the oxygen generated by the decomposition, a porous protective layer for detection electrode, which is formed so as to cover the detection electrode of the gas component-measuring means, and a harmful substance-trapping layer made of a porous material capable of trapping a harmful substance, which is formed apart from and upstream of the detection electrode, in a gas passage formed inside the solid electrolyte so as to enable the flowing of the to-be-measured gas, wherein the harmful substance-trapping layer is in contact with at least an upper surface of the gas passage and a lower surface of the gas passage, which are directly opposed to each other, and extends between the gas inlet and the first diffusion resistance portion and between the first diffusion resistance portion and the second diffusion resistance portion.