No matter how you set them up, thermal cameras are guaranteed to produce false negatives in four common situations:
- Anyone who is asymptomatic or pre-symptomatic
- Somoene who has taken medication to reduce their fever symptoms
- A person whose temperature is being taken while they are in or have recently been in cooler air temperatures
- Anyone who engaged in exercise within 10-15 minutes of having their temperature scanned or who was out in the cold
A Thermal Camera cannot detect people who are asymptomatic or pre-symptomatic because these people are not experiencing any symptoms. This means that they do not have a fever. You can’t screen for something that isn’t there.
People who are pre-symptomatic later develop symptoms, but they are still contagious and could pass the virus to others.
Current research estimates that between 25% and 80% of infected people could be “silent spreaders”. These are alarmingly high rates. None of these people would be flagged by a thermal camera.
Likewise, Thermal Cameras would not detect a fever in anyone who had reduced their symptoms by taking Tylenol and Advil.
Additionally, thermal cameras may also produce false negatives if people have recently exercised or were recently in colder weather. This is because they rely on measuring skin temperature rather than internal body temperature.