with secretions and via exhaled water droplets (Tellier, 2006). The former risk can be reduced by hygiene practices, such as hand washing and not touching one’s face; furthermore, the virus was found to survive at most several days on surfaces (Kampf et al., 2020). However, reducing the risk of virus transmission via droplets is complicated by the different particle sizes, which roughly range from larger droplets in the order of $100 \, \mathrm{\mu m}$ to smaller aerosol-size droplets in the order of $<1\, \mathrm{\mu m}$ (Tellier, 2006; Fabian et al., 2008). Larger particles ($>20  \, \mathrm{\mu m}$) have shorter settling times, i.e. they fall to the ground within seconds up to a few minutes. Smaller particles, however, may float in the air for hours and particles with a diameter $<3  \, \mathrm{\mu m}$ essentially do not settle (Tellier, 2006). Thus virus-contaminated droplets may accumulate in closed rooms such as workplaces or public transportation. Although at present it is not known how long the virus remains infectious, results by van Doremalen et al. (2020) indicate that the virus could survive several hours in aerosols-size droplets, and Asadi et al. (2020) conclude from their literature review that even the smallest aerosol-size droplets 