Effects of mask-wearing on the inhalability and deposition of airborne SARS-CoV-2 aerosols in human upper airway – American Institute of Physics

“It is natural to think that wearing a mask, no matter new or old, should always be better than nothing. Our results show that this belief is only true for particles larger than 5 micrometers, but not for fine particles smaller than 2.5 micrometers,” said author Jinxiang Xi.

The researchers found that wearing a mask with low (less than 30%) filtration efficiency can be worse than without.