I read advertising copy for several UV-C light air purifiers. I understand the science, but was still stunned.
In most cases the copy begins by describing how UV Light is dangerous to humans and can cause cancer and other panic-worthy conditions. It then describes how UV light can generate ozone, and overexposure to ozone is toxic and can be fatal. Several descriptions then described the fatality of Gamma and X Rays, and cautioned against human exposure to either. I expect a typical expert with graduate degrees from Google University headlines to be frightened.
Further down the page, following intervening text hyping the deadliness of UV, comes the real information. UV Light is short wave length, with separate bands labeled A, B and C. UV-A and UV-B cause sunburn and can cause skin cancer and eye damage, but UV-C does none of these things. It kills viruses and has been used for that for the past half-century. The cheaper and older the light source, the more likely it is to produce ozone. Modern UV-C light sources of even mediocre quality produce little ozone, certainly less than would harm a human. Better ones produce none.
I did learn something: Not all advertised UV-C light virus purifiers contain a UV-C light source. That is sold separately.