If the temperature of the outside environment is very different from the temperature of the measurement environment (both above and below), we must isolate people in a specific waiting area for 5-10 minutes before measuring the temperature.
In fact this is another reason why the installation of these systems outside is not recommended: a very cold or very hot environment not only does NOT constitute a constant and reliable calibration reference, but also has a considerable influence on the temperature of the skin, the radiation of which forms a barrier between the chamber and the actual radiation of the human body.
In short, the quality of the installation and the measurements goes up from option 1 to the following ones:
1) outdoor installation
2) outdoor installation on "thermalized" persons
3) outdoor installation with blackbody
4) outdoor installation with blackbody on "thermalized" persons
5) outdoor but covered installation
6) outdoor but covered installation on "thermalized" persons
7) outdoor but covered installation with blackbody
8) outdoor installation but covered and with blackbody on "thermalized" people
9) indoor installation
10) indoor installation on "thermalized" people
11) indoor installation with blackbody
12) indoor installation with blackbody on "thermalized" people (best case)
The word "thermalized" comes from quantum physics and we use it improperly to indicate a person who has expected those 5-10 minutes before making the measurement on the camera, adapting to the measurement environment and reducing as much as possible the influence of the external environment or of the newly made physical activity.