Experimental analysis to quantify inactivation of microorganisms by Far-UVC irradiation in indoor environments.

Far-UVC irradiation at a 222 nm wavelength is a promising technology for inactivating microorganisms in indoor environments to mitigate transmission of infection. Here we report experimental measurements in a room-scale chamber to evaluate the performance of filtered Krypton-Chloride (KrCl) lamps in reducing the steady-state concentration of Staphylococcus aureus and Pseudomonas aeruginosa under different ventilation rates in indoor environments. The results showed a mean 95.5 % lowering of S. aureus load and 94.9 % of P. aeruginosa load at 3 air changes per hour (ACH) using one Far-UVC lamp and 97.8 % and >97.5 % using five lamps. At 1.5 ACH, the mean microbial reduction for S. aureus was >94.6 % and >99.5 % and at 9 ACH, it was 66.3 % and 91.9 % for 1 lamp and 5 lamps, respectively. Initial results at a shorter distance between the microbial source and collection sampling show a reduced but still substantial effect of the Far-UVC. The findings indicate that within these experimental conditions, Far-UVC can be effective at room-scale inactivation of a range of pathogens in a range of ventilation scenarios and also show promise at short-range inactivation. This research paves the way for future work to explore efficacy in real-world scenarios and to quantify usability and acceptability.