A portable electrochemical or combustible lower explosive limit gas sensing apparatus includes a housing comprising at least one exterior surface and an interior space. At least one depression is formed in the at least one exterior surface and is adapted to accommodate, at least in part, components of an electrochemical gas sensor or a combustible LEL gas sensor. A processing unit is disposed in the interior space of the housing and is in electrical communication with the electrochemical gas sensor or the combustible LEL gas sensor.