Question about 1Temp 3 in 1 Infrared

The units are calibrated ex works. The manufacturer advises against doing your own calibrations, as very many factors play a decisive role. The sensor (the "little window" at the front) must be absolutely clean, there must be no draughts, the object to be measured must be at a perfect temperature, the measuring distance must be maintained, etc. I have also had the message that the measurement did not work. Mostly it was because I didn't aim correctly or quietly, or the sensor wasn't completely clean (wipe with a soft, dry cloth).
The calibration is described on this page (I didn't try it out because my device measures correctly). Apparently the manufacturer is aware that you can accidentally "mess up" the calibration:
https://www.ecotao-store.co.za/shop...
There, in the section/tab "Instruction" (under the product pictures) the calibration is described:
"Do not change the default settings. However, people sometimes inadvertently change the default factory setting. For calibration of the unit, switch on and hold the MODE key until F1 appears on the screen. Then, press the mode screen again. The screen will switch from F1 to F2. Pressing the up or down arrows will increment the temperature setting by 0.1 degree Celsius."

I don't know of anything that can be calibrated in this price range.
At the fire brigade, we have much higher-quality devices, but they are calibrated industrially.
That is not possible with this device.