The influence of ventilation on airborne transmission between stacking toilets

Multiple COVID-19 outbreaks in high-rise residential buildings have been linked to the vertical spread of the virus along the building. This study aimed to provide empirical evidence and experimental results to evaluate the effects of toilet ventilation on the spread of bathroom aerosols in high-rise residential buildings. This study explored potential transmission pathways by conducting tracer gas experiments in a full-scale mock-up toilet facility and identified effective strategies to minimize tracer gas surge and overall exposure. A novel IoT-enabled tracer gas sensing network was used to evaluate tracer gas dispersion from a lower-floor toilet to an upper-floor toilet and the roof under 32 different ventilation conditions of windows, exhaust fans, and forward-facing wind. The findings confirmed the potential for vertical airborne transmission through toilet ventilation and suggested effective ventilation strategies for forward-facing wind and no-wind conditions. This study provided novel experimental results on vertical aerosol transmission, contributing to further analysis and validation in this field. Appropriate ventilation measures were also discussed to ensure clean, virus-free air intake, reducing the risk of airborne cross-infection via the vertical transmission pathway.