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Filtration Efficiency and Inhalation Resistance of Cloth Mask Combinations and the Effects of Washing and Drying On Performance
SUMIT SANKHYAN, Karen Heinselman, Peter Ciesielski, Hannah Teed, Teresa Barnes, Sameer Patel, Marina Vance, University of Colorado Boulder
Abstract Number: 100
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
In this study, filtration efficiency of different respirators, masks, and face coverings for particles in the size range of 60 nm - 4 μm was investigated under a “perfect fit” condition using two experimental setups. The filtration efficiency at the most penetrating particle size of 0.3 μm on average ranged from 90-99% for N95 and KN95 respirators, 40-88% for surgical masks, and 9-51% for cloth masks and a 2-ply bandana. We also investigated the effects of doubling surgical masks or layering a cloth mask over a variety of surgical masks, as this seems to have become a popular approach during the COVID-19 pandemic. For most combinations, the filtration efficiency improved by ~25% for particles 0.3-1 μm in diameter without any substantial change in the filter quality factor. To investigate the reusability of cloth masks, 2-layer cotton fabric samples were washed and dried for 52 cycles and, while this process led to an increase in inhalation resistance (~20 Pa), the size-resolved filtration efficiency did not change noticeably. Electron microscopy analysis revealed that washing and drying led to a deconstruction of individual fibers at the scale of several microns to hundreds of nanometers in the form of delamination of the fiber wall and fibrillation of the nanofiber constituents. The results from this study can be useful for understanding the sustainability of cloth masks and the relative protection of different masks and layering strategies to reduce both PM2.5 exposure the risk of respiratory disease transmission.