https://thenextweb.com/science/2021/02/13/temperature-scanners-wont-stop-covid-19-syndication/

During the pandemic, the chances are that as you enter an airport or doctor’s surgery, someone will point an infrared thermometer at your forehead in order to assess your temperature. Your skin temperature is being measured to try to identify whether or not you have an increased deep body temperature, which is indicative of fever, one of the leading signs of COVID-19.

The good thing about using infrared thermometers is that they are quick, simple, and non-invasive. You can rapidly screen many people without inconveniencing them, for instance, travelers moving through an airport or people entering a sports stadium. But to be useful mass-screening tools, infrared thermometers also need to be accurate – and this is where problems arise.