A method and apparatus for maintaining a viewing window of a detector substantially clean includes enclosing the detector within a housing, and moving a target surface relative to the viewing window to create an airflow adjacent the viewing window. The housing can include an aperture through which the viewing window of the sensor views the target surface. Motion of the target surface creates an airflow velocity adjacent the viewing window for maintaining the viewing window substantially clean. To increase the accuracy of the detector, a high emissivity area is provided on an outside surface of the housing which faces the target surface.