As UV-C provides radiation - IT IS NOT SAFE TO BE IN ROOM WITH UV-C while disinfection is taking place. UV-C is classified as "reasonably anticipated to be a human carcinogen by the National Toxicology Program. UV-C light is harmful for skin and eyes, do direct exposure to UV-C is aways to be avoided. UV-C is blocked by a number of materials, including glass (except quartz glass) and most clear plastics, so it's possible to safely observe a UV-C system if you are looking through a window. UV-C provides residue free disinfection so there's no concern over dangerous residues that are used to be wiped down or neutralize after the disinfection occurs.