Reflection of UVC wavelengths from common materials during surface UV disinfection: Assessment of human UV exposure and ozone generation

• Published in: The Science of the total environment 2023-04, Vol.869, p.161848-161848, Article 161848
• Main Authors: Ma, Ben, Burke-Bevis, Sam, Tiefel, Luke, Rosen, Jennifer, Feeney, Ben, Linden, Karl G.
• Format: Article
• Language: English
• Subjects: 222 nm; 254 nm; COVID-19; Disinfection - methods; Far UVC; Humans; Krypton chloride (KrCl) excimer; Ozone generation; Pandemics; Reflection; Safety assessment; Skin; Ultraviolet Rays
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.161848

The COVID-19 pandemic has promoted interest in using devices emitting ultraviolet-C (UVC) irradiation (200–280 nm) for surface disinfection to reduce pathogen transmission, especially in occupied public spaces. While UVC devices have been shown to be highly effective against various pathogens, there are safety concerns when using conventional UVC devices for surface disinfection, including human exposure of reflected UVC irradiation and ozone generation. Emerging Far UVC devices (emitting at 200–230 nm), like the krypton chloride (KrCl*) excimer, have the potential to be safely applied in occupied spaces due to their minimal adverse effects on skin and eyes. In this study, UV reflection of 21 common materials was documented and compared using a filtered KrCl* excimer (installed with a bandpass filter at 222 nm), an unfiltered KrCl* excimer, and a conventional low-pressure mercury vapor lamp. The safety of Far UVC devices was evaluated based on the irradiance and spectrum of reflected UV irradiation and ozone generation measured at various locations around the device. Our results show that most common materials can reflect UV irradiation, among which some metals tend to have greater reflection. The Far UVC devices, especially the filtered KrCl* excimer, should be safe to be applied in occupied spaces for effective surface disinfection, with limited ozone generation and no health risk from reflected UV irradiation. However more caution is needed when using unfiltered KrCl* devices and conventional UV 254 nm light. This study provides urgently needed data on UV reflection of common materials and guidance for safety assessments of UVC devices for surface disinfection in occupied spaces. [Display omitted] •Common materials can reflect UV, among which metals have greater reflection.•Filtered KrCl* excimer is safe and effective for surface disinfection.•Reflected UV for unfiltered KrCl* excimer and Hg lamp exhibit greater health risks.•Ozone generation by UV lamps is unlikely to cause health risks.