Gas sensor

The utility model discloses a gas sensor, which includes a housing with a liquid storage cavity, a bottom steel disc, an upper gasket, a lower gasket and a gas electrochemical reaction component. A rubber sealing ring is arranged inside the housing, a first concave steel disc is accommodated in the rubber sealing ring and provided with an air inlet, and a prominent internal pressure-line and a prominent exterior pressure-line are formed at the bottom of the rubber sealing ring; the bottom steel disc is held at the upper part of the liquid storage cavity and provided with a through hole; the upper gasket and the lower gasket are arranged between the rubber sealing ring and the bottom steel disc, and a hot-melting rubber layer is arranged between the lower gasket and the bottom steel disc; and the gas electrochemical reaction component is arranged between the upper gasket and the lower gasket. By adopting the pressure transmission between the exterior pressure-line and the interior pressure-line and arranging t