Vertical transmission of aerosols in building drainage pipes: A review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be transmitted through fecal aerosols in building drainage pipes (BDS) has been demonstrated, so there is an urgent need to understand its specific transmission pathways and mechanisms. This paper reviews the two periods of vertical transmission of aerosols in BDS: airflows caused by pressure fluctuations during toilet flushing and airflows induced by the chimney effect. Subsequently, recent advances in research methods and factors affecting the vertical transmission of aerosols in BDS are discussed. Finally, we conclude the vertical transmission pathway of aerosols in BDS as “bathroom - drainage pipe - failed floor drain – bathroom”. Additionally, more consideration needs to be given to the driving force brought on by the chimney effect when the transient pressure created by toilet flushing dissipates. Further study is imperative to establish a quantitative understanding of the relative importance and duration of aerosol vertical transmission effects during these two periods. Overall, both designers and academics can utilize this review as a reference to mitigate the potential risk of vertical transmission of aerosols in BDS, so that BDS can be appropriately designed to minimize pressure fluctuations and the water seals in floor drains can be regularly checked.