Fig. 4. Filtration efficiency of 47 commercially available masks.

a Filtration efficiency for all aerosols of 0.2 μm and larger, shown with a regulation-tested N95 mask (blue marker) at a face velocity of 10 cm/s, roughly simulating an 105 LPM inspiratory breathing rate; and b mask performance shown for three aerosol size fractions from 0.2 to 1 μm. Efficiencies shown are determined via aerosol number concentrations and the a inset shows variations across masks tested for four mask types, displayed as the absolute deviation in aerosol filtration efficiency from the average (i.e., Eff._{Sample i} − Eff._Avg.). Mask numbers in the inset (and Fig. 5) refer to cataloging in Table S1 and not rank-ordered performance.