In a recent published study of microscopic surface morphology and filtering efficiency of face masks it was concluded that the “Filtering efficiency of CM (cloth masks) was poorer than in SM (surgical masks). The poor efficiency was due to the presence of larger sized pores.”
“Our study also demonstrated that washing and drying cycles deteriorates the filtering efficiency due to change in pore shape and clearance. We also found that stretching of the CM surface alters the pore size and potentially decreases the filtering efficiency. The findings of this study suggest that CM are not effective, and that effectiveness deteriorates if used after washing and drying cycles and if used under stretched condition. We believe that the findings of this study will be helpful for increasing public awareness among populations of developing countries where such masks are very common, and for policy makers to make and implement basic guidelines for face masks for public use.”