Duke University tests mask effectiveness
Researchers at Duke University used a simple test on 14 different types of face coverings to determine which are most effective.
The most effective was the fitted N95 mask without valve. Three-layer surgical masks and cotton masks also performed well.
At the other end of the spectrium, folded bandannas and knitted masks performed very poorly, while neck fleeces (also called gaiter masks) resulted in a higher number of respiratory droplets than wearing no mask at all.
“Low-cost measurement of facemask efficacy for filtering expelled droplets during speech” by: Emma P. Fischer, Martin C. Fischer, David Grass, Isaac Henrion, Warren S. Warren and Eric Westman. Cite as: Fischer et al., Sci. Adv. 10.1126/sciadv.abd3083 (2020).