Design a infrared temperature sensor enclosure / housing

I need a 3D design (printable) for a Infrared Thermopile Sensor enclosure (housing). The problem is that the PCB on which the sensor is mounted must be optimally protected against three threads: a) heat radiation, b) hot air convection, and c) pollution by steam and smoke. The reason is: a) an b) can heat up an unprotected PCB too fast which results in a huge error in the infrared energy measurement. And c) leads to a reduction of infrared radiation that must reach the sensor surface and not be absorbed by a layer of pollutant. The surface of the sensor cannot be covered by glass or other material, because most materials are not transparent in the range of 4 to 16 Micrometers (far-infrared). The sensor chip is tiny (1.9 x 1.9 mm, height 0.6 mm. It is mounted on a breakout board like the one shown in the image (appended - chip visible in the center of the board). This project is about designing the optimal, printable 3D geometry of the sensor's housing, and suggest the materials (for instance surface coating) to minimize the threads by a), b) and c).