Ultraviolet (UV) C light emitted by a krypton chloride (KrCl) lamp consists of mainly less harmful 222-nm Far-UVC (unfiltered 222-mm Far-UVC) compared with conventionally used 254-nm UVC. It also contains wavelengths that are harmful to mammalian cells. By contrast, UVC from a KrCl lamp with optical filter (filtered 222-nm Far-UVC) consists of much less harmful 222-nm Far-UVC and is available for sterilization of dwelling spaces. The germicidal mechanisms of the 254-nm UVC and unfiltered 222-nm Far-UVC have been partially elucidated
however, the mechanism of action of filtered 222-nm Far-UVC remains unknown. It is known that 254 nm UVC induces cyclobutene pyrimidine dimers (CPDs), which are DNA lesions in