US Patent 7607340 Gas sensor

In a protector (100) for protecting a detecting portion (11) of a sensor element (10) of a gas sensor (1), the opening area of individual inner introduction holes (130) and (140) formed in an inner protector (120) is 3.5 mm2 or less. In this manner, the amount and size of water droplets able to pass through the inner introduction holes (130) and (140) and to adhere to the sensor element (10) is restricted. In order to ensure good gas replaceability between the interior and the exterior of the inner protector (120) so as to attain quick gas response, the total opening area of the inner introduction holes (130) and (140) is 10 mm2 or more.