This is also of current significance as the relative effectiveness of different droplet sizes in transmitting the SARS-CoV-2 virus is not clear, and understanding the filtration response across a large bracketed size distribution is therefore important. However, there is limited data available today on the performance of common cloth materials used in such cloth masks, (7−12) particularly their filtration efficiencies as a function of different aerosol sizes ranging from ∼10 nm to ∼10 μm scale sizes. (3−6) The use of such masks is also an anticipated response of the public in the face of future pandemics related to the respiratory tract. The use of cloth masks, many of them homemade, (1,2) has become widely prevalent in response to the 2019–2020 SARS-CoV-2 outbreak, where the virus can be transmitted via respiratory droplets. Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles. Our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60% decrease in the filtration efficiency, implying the need for future cloth mask design studies to take into account issues of “fit” and leakage, while allowing the exhaled air to vent efficiently. Cotton, the most widely used material for cloth masks performs better at higher weave densities ( i.e., thread count) and can make a significant difference in filtration efficiencies.
We speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration. Filtration efficiencies of the hybrids (such as cotton–silk, cotton–chiffon, cotton–flannel) was >80% (for particles 90% (for particles >300 nm). Although the filtration efficiencies for various fabrics when a single layer was used ranged from 5 to 80% and 5 to 95% for particle sizes of 300 nm, respectively, the efficiencies improved when multiple layers were used and when using a specific combination of different fabrics. We have carried out these studies for several common fabrics including cotton, silk, chiffon, flannel, various synthetics, and their combinations. Importantly, there is a need to evaluate filtration efficiencies as a function of aerosol particulate sizes in the 10 nm to 10 μm range, which is particularly relevant for respiratory virus transmission.
However, there is limited knowledge available on the performance of various commonly available fabrics used in cloth masks. This includes the use of cloth masks by large sections of the public, as can be seen during the current global spread of COVID-19. The emergence of a pandemic affecting the respiratory system can result in a significant demand for face masks.
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