Gas concentration detection sensor

A gas concentration detection sensor, comprising:

• a sensor element that detects concentration of a selected gas included in an object gas;
• a first protection cover that covers over the sensor element and has a first gas introduction aperture allowing for a flow of the object gas from outside to inside of the first protection cover;
• a second protection cover that covers over the first protection cover and has a second gas introduction aperture allowing for a flow of the object gas from outside to inside of the second protection cover;
• a gas flow path that runs from the second gas introduction aperture through a space between the first protection cover and the second protection cover to the first gas introduction aperture, enters inside of the first protection cover via the first gas introduction aperture, and reaches an edge of the sensor element,
• wherein at least one of the first protection cover and the second protection cover is provided with an inner wall member of a solid form or a hollow form that creates an internal enclosed space arranged to at least partially narrow a width of a flow path from the second gas introduction aperture to the first gas introduction aperture
• wherein the first protection cover has a first gas discharge aperture that is formed in a circumferential wall of the first protection cover at a lower position than the edge of the sensor element, the second protection cover has a second gas discharge aperture formed in a bottom face of the second protection cover, and
• the object gas reaching the sensor element passes through the first gas discharge aperture by a radially outward flow in a direction from a center to an outer circumference of the first protection cover and is discharged out via the second gas discharge aperture.