Effectiveness of 222 nm far-UVC disinfection of airborne and surface bioaerosols in railway trains

Since urban residents heavily rely on rail transit on a daily basis, controlling airborne infectious disease transmission in railway trains is critical for public health. In recent years, 222 nm far-ultraviolet C (UVC) lamps have emerged as a promising solution for disinfection of bioaerosols in occupied environments with enhanced safety. However, there is a lack of experimental data in railway train compartments, especially regarding the effectiveness of far-UVC against bioaerosols that are suspended in the air and that settle on handrails. Therefore, this study experimentally and numerically evaluated the effectiveness of far-UVC disinfection of bioaerosols suspended in air and deposited on surfaces using a simplified, scaled railway carriage model. The experimental data show that, under a high ventilation rate of 107 air changes per hour (ACH), the far-UVC lamp still provided supplementary reduction of viable airborne bioaerosols, achieving a disinfection efficiency of 23% to 52% for Escherichia coli (E. coli) in the breathing zone of the manikins. Furthermore, exposure to far-UVC resulted in a marked decrease in viable E. coli measured on handrail surfaces, with reductions ranging from 23% to 78%. After validation by the experimental data, the numerical model was applied to a full-scale railway cabin representative of Hong Kong operations to assess far-UVC effectiveness against SARS-CoV-2 bioaerosols suspended in the air and deposited on internal surfaces. Model predictions showed that exposure to far-UVC resulted in a 17%–25% reduction in viable bioaerosol concentrations within passenger breathing regions. A 39% reduction in viable SARS-CoV-2 bioaerosols was observed on handrails.