welding the air cover to the housing over the overlap the welding is accomplished while pressing the air cover against the housing thereby compressing an elastic member in the air cover to establish a hermetic seal between the sensor element and the housing application_number US 65465207 A description referring to the drawings wherein like reference numbers refer to like parts in several views particularly to fig1 there is shown a gas sensor 1 according to the first embodiment of the invention which may be employed in a burning control system or air fuel ratio control system of an automotive vehicle to measure concentrations of components such as nox co hc and o 2 contained in exhaust gasses of the engine the gas sensor 1 generally includes a sensor element 2 a first insulation porcelain 12 a second insulation porcelain 11 a hollow cylindrical housing 19 and an air cover 10 the sensor element 2 is made of a laminated plate consisting of a solid electrolyte body ceramic layers and electrode layers for example u s pat no 5 573 650 issued on nov 12 1996 to fukaya et al teaches a typical laminated sensor element disclosure of which is incorporated herein by reference the second insulation porcelain 11 is made of a hollow cylindrical member and is fitted within the housing 19 and holds therein the sensor element 2.