Modeling the vertical transmission of bioaerosols in residential building drainage systems

The vertical transmission of bioaerosols in building drainage systems is an understudied route of disease spread. This research examines how the position of drainage floors, flush volume, pipe type, and building story number affect the dynamics and reach of bioaerosols in such systems. Our findings show that drainage points positioned lower in a building amplify the number of the affected floors above, with recorded pressure differences at various drainage points ranging from 900 to 3200 Pa, depending on flush volume and floor position. The transition to a double pipe system significantly reduced pressure differences (to as low as 330 Pa in vent pipes), thereby diluting bioaerosol concentrations but increasing their dispersion across more floors. Building story number further influenced bioaerosol spread, with higher buildings exhibiting negligible pressure differences across stories (1400–2300 Pa) but a pronounced increase in affected floors above the drainage site.