Yet another security theater
Bruce Schneier linked to an interesting essay about mass screening of people with infrared thermometry guns. With this devices you can measure the temperature of a person from a certain disctance. But the essay questions the sense of such a method as they compared the results of this IR guns with :
We assessed the accuracy of cutaneous infrared thermometry, which measures temperature on the forehead, for detecting patients with fever in patients admitted to an emergency department. Although negative predictive value was excellent (0.99), positive predictive value was low (0.10). Therefore, we question mass detection of febrile patients by using this method.
Negative predictive value means “The device says you have no fever and you have really no fever”. Negative predictive value stands for “The device says you have fever, and you have really fever.” So the system is good at detecting a person without fever, but not at dividing people with a higher (but normal for them) skin temperature and people with fever.