Fig. 2.

1D simulations on evaporating droplets assuming stagnant ambient air. (a) Evaporation time, i.e. Wells curve, for water. (b) Sedimentation time of water droplets with non-volatile content. The shaded areas indicate the sedimentation time range. Clearly, all droplets in the considered range of below $200\mathrm{\mu }$m could stay airborne, and hence to be inhaled, as $\mathit{St}\ll 1$ and ${\tau }_p\ll t_s$. This is particularly true for droplets below 100 $\mathrm{\mu }$m.