A Novel Bioaerosol Chamber to Measure the Inactivation Rate of Airborne Viruses at Low Far-UV-C Radiation Doses

Abstract 222 nm Far-UV-C light is considered an effective technology to inactivate airborne viruses in indoor environments, even while being occupied by humans. This is due to the safer characteristics of 222 nm UV-C light, which has much higher exposure limits as compared to the more traditional 254 nm UV-C. Several studies have reported on the susceptibility of viruses in laboratory aerosol chambers. Unfortunately, the chambers used in these studies have complex air-flow characteristics and non-uniform UV irradiance, resulting in a large variability in the calculated dose of the UV. In this study, we report the design and construction of a novel UV-C exposure chamber, with a well-defined laminar flow profile and nearly uniform UV-C irradiance across the aerosol path. This was done by using pairs of UV-C lamps on both sides of the virus aerosol flow. The new Far-UV-C exposure chamber provides a simpler UV dose calculation with less variability, resulting in more accurate virus inactivation rate measurements. We demonstrated the use of the new chamber for the inactivation of HCoV-OC43 betacoronavirus (a surrogate for SARS-CoV-2) at low Far-UV-C doses. We found an HCoV-OC43 virus inactivation rate of 6.51 ± 1.69 cm 2 mJ −1 (95% CI), that can be used for designing Far-UV-C disinfection systems for continuous operation at low doses of 222 nm UV-C light. We have also measured the ozone generation rate for the lamps used in our new exposure chamber; we conclude that these lamps can be safely used with minimum ozone generation (49.9 ± 9.8 µg h −1 ) in indoor environments. Graphical abstract