Induced airflow and particle exposure to a standing adult after flushing a urinal in a lavatory

Urinals are widely used in men's public lavatories. Flushing a urinal can create a strong waterflow that sweeps the urinal surface and causes the emission of aerosols. To date, both the water-induced airflow and the likelihood that the aerosols released from the urinal will be inhaled by the user remain unknown. This study investigated the flushing waterflow, the water-induced airflow, and the aerosol transmission with the use of computational fluid dynamics modeling. The two-phase water–air flow was modeled by the volume-of-fluid method, while the aerosol transport was resolved by the drift-flux model, after validation of the models by measurement data. The possible inhalation exposure to the aerosols by the urinal user was inferred. The effects of the urinal's installation height, the initial water level in the urinal bowl, and the distance of the user from the urinal on the flushing-induced airflow and the aerosol inhalation exposure were analyzed. The results revealed that the flushing water can entrain the surrounding air to generate airflow jets at a speed of 0.5 m/s toward the urinal user. The airflow jets can travel a distance of at least 0.5 m and reach a height of 1.2 m. If the flushing-induced airflow is intercepted by the torso, the airflow can carry the aerosols into the breathing zone within 5 s. A urinal installed at a lower height, a user standing closer to the urinal, or a higher water level maintained in the bowl, can minimize inhalation exposure to the aerosols released from the urinal.