Infrared thermometers can be calibrated for accuracy just like other thermometers. In ETI's Calibration Laboratory technicians use industrial black bodies to calibrate infrared thermometers with certification traceable to National Standards. UKAS accredited certification of IR Thermometers may be obtained from ETI on application and quotation. Black bodies approximate zero reflected ambient radiation and therefore the unimpeded emission of infrared energy for a given emissivity value, typically 0.95.
Without having access to a black body, the next best way to calibrate your infrared thermometer is to use a simple, inexpensive Infrared Comparator Cup. It is best to calibrate your infrared thermometer at more than one temperature (at 5°C and 60°C] for example) and the Infrared Comparator Cup makes it easy.
If neither of these are available, you can do a quick calibration using a properly made ice bath.
Using a boiling point for calibration is more difficult with an infrared, factoring in variables in air pressure and elevation, are further complicated with infrared thermometers owing to the steam generated by boiling. That steam and the evaporative cooling and condensation that ensues makes it difficult to obtain an accurate infrared measurement of a boiling liquid. But the surface of a properly made ice bath is a dependable 0.0°C