Aerosol filtration testing of fabrics for development of reusable face masks

The ongoing outbreak of coronavirus disease of 2019 (COVID-19), triggered by the rapid community spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has brought forward the need for speedy testing and manufacturing of respiratory face masks for global use. Overwhelmed by the fast-growing demand for disposable face masks, many governments have recommended the use of, and elaborated design criteria for, reusable face masks that are meant to slow down the transmission of SARS-CoV-2 in the general population. Using aerosol particle size spectrometers, we performed particle size distribution measurements and calculated the fractional aerosol particle size-selective filtration efficiencies of over 300 fabrics and fabric-assemblies, including chiffon, cotton, synthetics, and various promising layered combinations. We suggest, and experimentally verify, a simple way for estimating the aerosol filtration efficiency of layered fabrics. The analysis herein investigates the relationship between the breathability and filtration properties of fabrics, assemblies of fabrics, and commercial reusable masks from various regions around the globe. In addition, we demonstrate how a hydrophobic coating can provide a statistically significant increase in the fabrics’ filtration efficiency. The insights of this work are crucial to developing non-woven, high-filtration-performance, reusable face masks that can be worn for extended periods of time.