Patent ID: 6949175

Claim:
A gas sensing element comprising: a solid electrolytic substrate having oxygen ion conductivity; a measured gas side electrode provided on a surface of said solid electrolytic substrate so as to be exposed to a measured gas; a reference gas side electrode provided on another surface of said solid electrolytic substrate so as to be exposed to a reference gas; and a single porous electrode protecting layer directly contacting and entirely covering said measured gas side electrode, wherein a limit current density of said electrode protecting layer is in a range from 0.04 mA/mm 2 to 0.15 mA/mm 2 on a unit area of said reference gas side electrode under the following conditions: an oxygen concentration in said measured gas is 0.1%, a measurement temperature and an element surface temperature at the measured gas side of a sensing portion are not less than 600° C., and a voltage applied between the measured gas side electrode and said reference gas side electrode is 0.5V.