Table 2.

Droplet falling time as a function of size and the corresponding air exchange rate

Droplet diameter ($\mathrm{\mu }\mathrm{m}$)	Falling time of 1 m (s)	Air exchange rate (${\mathrm{h}}^{-1}$)
1.0	29 070	0.12
2.5	5076	0.71
5.0	1311	2.75
10.0	333	10.81
20.0	84	42.86