A housing for a sensor having a semiconductor element for measuring hydrogen concentration in an insulating fluid in electric power generation, transmission, and distribution equipment having a mounting flange on the equipment providing access to the interior of the equipment and provided with a plurality of bolt receiving openings arranged on the mounting flange in a first pattern, comprising: (a) a first flange having at least one or more openings for receiving one or more semiconductor hydrogen sensors and an outer periphery; (b) a plurality of bolt receiving apertures arranged in a pattern corresponding to the first pattern within the outer periphery of the first flange; (c) a second flange having a second plurality of bolt receiving apertures arranged in a pattern corresponding to the first pattern within the periphery of the second flange; (d) a housing body (1 3) having one end thereof connected to the second flange, surrounding the one or more openings, disposed among the bolt receiving apertures, and spaced there from a sufficient distance to allow access to bolts disposed in the apertures for inserting and removing bolts from the apertures and having an outer periphery contained within the outer periphery of the first flange and further having a substantially uniform cross-section extending a distance from the second flange sufficient to accept the sensor wherein the second seal surrounds the sensor receiving openings (42, 44); (e) at least one wire receiving opening extending through the housing body; (f) a cover closing the end of the housing body (1 3) distal from the one end; (g) a first seal disposed between the first and second flanges (18, 23); (h) a second seal disposed on the first flange (1 8) for engaging the mounting flange wherein the second seal surrounds the sensor receiving openings (42, 44); and (i) a sampling and bleeding valve extending through the first flange in communication with the interior of the equipment and oriented so that, when opened, trapped gas will exit the valve. (a) a first flange having at least one or more openings for receiving one or more semiconductor hydrogen sensors and an outer periphery; (b) a plurality of bolt receiving apertures arranged in a pattern corresponding to the first pattern within the outer periphery of the first flange; (c) a second flange having a second plurality of bolt receiving apertures arranged in a pattern corresponding to the first pattern within the periphery of the second flange; (d) a housing body (1 3) having one end thereof connected to the second flange, surrounding the one or more openings, disposed among the bolt receiving apertures, and spaced there from a sufficient distance to allow access to bolts disposed in the apertures for inserting and removing bolts from the apertures and having an outer periphery contained within the outer periphery of the first flange and further having a substantially uniform cross-section extending a distance from the second flange sufficient to accept the sensor wherein the second seal surrounds the sensor receiving openings (42, 44); (e) at least one wire receiving opening extending through the housing body; (f) a cover closing the end of the housing body (1 3) distal from the one end; (g) a first seal disposed between the first and second flanges (18, 23); (h) a second seal disposed on the first flange (1 8) for engaging the mounting flange wherein the second seal surrounds the sensor receiving openings (42, 44); and (i) a sampling and bleeding valve extending through the first flange in communication with the interior of the equipment and oriented so that, when opened, trapped gas will exit the valve.