Experimental study on enhancing single-pass air disinfection efficacy for portable disinfection systems with different Far-UVC sources

Two single-pass air disinfection systems utilizing different form factors of Far-UVC sources were designed to achieve indoor air disinfection. The first system, namely the external-module-equipped (EME) system, featured a rectangular UV source module attached to the envelope of the disinfection box chamber. The second system, known as the internal-tube-equipped (ITE) system, incorporated a centrally positioned UV tube within the chamber. To assess their air disinfection efficacy, two bacteria, Salmonella enterica and Staphylococcus epidermidis, and one bacteriophage, MS2 were selected as challenges for the systems operating at a flow rate over 100 m 3 /h. The baseline EME system inactivated the microbes with the efficacies of 81.4 %, 16.9 %, and 25.1 % for S. enterica, S. epidermidis, and MS2, respectively. In comparison, the baseline ITE system demonstrated higher inactivation efficacies due to a wider irradiated area, with respective efficacies of 94.4 %, 25.8 %, and 37.8 % for the tested microorganisms. Two enhancement measures were implemented by redirecting airflow to the areas with high UV irradiance and enhancing UV reflectance, increasing the inactivation efficacy of the systems by up to 207.0 %. When tested against Staphylococcus epidermidis, compared with an upper-room Far-UVC, the modified EME and ITE systems presented an increase in inactivation rate by 23.0 % and 29.2 % respectively. These results demonstrated the potential of the systems to efficiently and sustainably inactivate a broad spectrum of microbes in future practical applications.