Gas sensor

A gas sensor comprising:

• a sensor element having a gas inlet through which measurement-object gas is introduced and capable of detecting a concentration of a predetermined gas in the measurement-object gas that flows into the sensor element through the gas inlet;
• an inner protective cover that has a sensor element chamber thereinside and in which one or more element-chamber inlet and one or more element-chamber outlet are arranged, the sensor element chamber accommodating a front end of the sensor element and the gas inlet, the element-chamber inlet being an entrance to the sensor element chamber, and the element-chamber outlet being an exit from the sensor element chamber;
• and
• an outer protective cover disposed outside the inner protective cover and including a body portion, which has a cylindrical shape and in which one or more outer inlet is arranged, and a front end portion, which has a cylindrical shape with a bottom and an inner diameter smaller than an inner diameter of the body portion and in which one or more outer outlet is arranged, the outer inlet being an entrance from outside for the measurement-object gas, and the outer outlet being an exit to the outside for the measurement-object gas,
• wherein the outer protective cover and the inner protective cover form a first gas chamber as a space between the body portion of the outer protective cover and the inner protective cover and a second gas chamber as a space between the front end portion of the outer protective cover and the inner protective cover, the first gas chamber being at least a portion of a flow channel for the measurement-object gas between the outer inlet and the element-chamber inlet, and the second gas chamber being at least a portion of a flow channel for the measurement-object gas between the outer outlet and the element-chamber outlet and not being directly connected to the first gas chamber,
• the element-chamber inlet is formed in the inner protective cover so that an element-side opening of the element-chamber inlet that is adjacent to the sensor element chamber opens in a forward direction, which is a direction from a back end toward the front end of the sensor element,
• the outer inlet includes a horizontal hole arranged in a side portion of the body portion of the outer protective cover, and
• the outer outlet is not arranged in a side portion of the front end portion of the outer protective cover.