Where you sit on a public bus, train or subway can determine your level of exposure to exhaled droplets, including those that may be carrying COVID-19, according to a new study.

Published in the peer-reviewed journal Physics of Fluids, the study analyzed what happens when speech droplets are exhaled from a row of sitting passengers in a ventilated space, such as those found in public transit vehicles.

In the ventilation systems of some of these spaces, air is injected at the top and extracted at the bottom through vents near the windows. The researchers found droplets after exhalation from passengers sitting in window seats rose more and invaded the space of other passengers to a lesser degree.

In addition, droplets from middle-seat passengers contaminated aisle-seat passengers more than window-seat passengers. Droplets released from passengers in aisle seats were dragged down by the ventilation system immediately.

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