GAS SENSOR

To suppress the decrease in sensitivity to second particular gas.SOLUTION: A sensor element 110 includes a detection unit 23 that detects the concentration of first particular gas, and a mixed potential cell 55 that generates electromotive force according to the concentration of second particular gas. A detection electrode 56 of the mixed potential cell 55 is covered with a buffer layer 84 and a protection layer 85. An inner protection cover 130 includes first entrances 125 and second entrances 127 as element chamber entrances 123. In a virtual projection diagram in which a first member 131 and a sensor element 110 are projected vertically on a virtual plane perpendicular to an axial direction of the first member 131, at least one of the first entrances 125 is disposed so that the angle θ between a first straight line S1 drawn from a center X of an arrangement surface 56a of the detection electrode 56 to the opposite side of an element main body 20 in a direction perpendicular to the arrangement surface 56a and a second straight line S2 drawn from the center of the arrangement surface 56a to a center of the first entrance 125 is 73.6° or less.SELECTED DRAWING: Figure 9 【課題】第２特定ガスに対する感度の低下を抑制する。【解決手段】センサ素子１１０は、第１特定ガスの濃度を検出する検出部２３と、第２特定ガスの濃度に応じた起電力を生じる混成電位セル５５と、を備えている。混成電位セル５５の検知電極５６は、緩衝層８４及び保護層８５で覆われている。内側保護カバー１３０は、素子室入口１２３として、第１入口１２５及び第２入口１２７を有している。第１入口１２５のうちの少なくとも１つは、第１部材１３１の軸線方向に垂直な仮想平面に第１部材及１３１及びセンサ素子１１０を垂直投影した仮想投影図において、検知電極５６の配設面５６ａに垂直で配設面５６ａの中心Ｘから素子本体２０とは反対側に引いた第１直線Ｓ１と、配設面５６ａの中心から第１入口１２５の中心に向けて引いた第２直線Ｓ２と、のなす角度θが７３．６°以下となるように配置されている。【選択図】図９