The Dispersion and Exposure to Aerosols From Toilet and Urinal Flushing Under the Effect of Closing Toilet Lid and Different Ventilation Rates in a Public Washroom

Abstract

Abstract Water flushing in the washroom can release many fecal and urine aerosols, which may contain contagious viruses if the users are infected, such as norovirus, influenza, and COVID-19. However, the dispersion of fecal and urine aerosols and exposure of healthy users were less studied in public washrooms. This study employed computational fluid dynamics (CFD) simulations to investigate aerosol dispersion and inhalation exposure in a public washroom under various situations, including closing the toilet lid, different aerosol sources, user locations, and ventilation rates. For the studied public washroom with negative pressure ventilation, the toilet and urinal aerosols were not well mixed because of the blocking effect of cubicles and the suction of the exhaust. It formed a primary airflow from the door gap to the ceiling exhaust. The users upstream of the aerosol source (i.e., the door region) had a lower exposure than others. The simulation results indicated that closing the toilet lid could reduce the exposure of distant users by 90% due to enhanced deposition on the toilet bowl, but it increased the exposure of nearby users. Installation of local exhausts in the cubicles reduced the average exposure by 13%. Increasing the ventilation rate from 2 to 15 can significantly reduce the intake fraction from 1 × 10–3 to 0.4 × 10–3 with a reduction ratio of 60% for the toilet and urinal flushing. The intake fraction from closed toilet lid flushing was almost independent of the ventilation rate, which had a value of around 0.2 × 10–3. This study enhanced our understanding of infection spread in public washrooms affected by multiple factors. Graphical Abstract

Keywords

• Sanitary facilities
• Water flushing
• Toilet lid
• Intake fraction
• COVID-19