The invention relates to a gas analyzer comprising a measuring volume (6) for a sample gas mixture (G), a radiation source (1) for providing a beam (20) of electromagnetic radiation to pass said measuring volume, a heat sink (4) for said radiation source, at least one thermopile detector (9), at least one optical bandpass filter (10), electrical contact pins (12) for signal(s) in the housing of said detector, a thermal mass formed of a material having high thermal conductance. Said thermal mass has a cavity (21) and an outer surface (22), surrounding at least said detector housing in the cavity, being in contact with said detector housing, and extending towards the radiation source. There is a thermal barrier between the heat sink (4) and the thermal mass (8, 16). The gas analyzer further comprises electrical wires (15), which are composed of materials and having dimensions producing an overall thermal conductance substantially lower than that of said electrical contact pins. Said wires are connected with the electrical contact pins either directly or indirectly, and enclosed in the thermal mass together with said detector housing(s), and extend from the cavity through the thermal mass (8, 16) to the outside thereof.