So because of some turn of events, I was enrolled in a privately owned school in Shenzhen, China, around the year of 2010, for a year.

In the primary school, all classes have UV lights to kill germs. So upon leaving the class, the last student would turn off the (normal) lights and turn on the UV lamps. In the morning they would ofc turn off the UV lamps and turn on the normal lighting.

I'm not gonna talk about efficacies or whether it causes harm, it might as well be placebos, but from what I know, it's kind of common to have.