Based on these findings, we recommend a three-layer mask consisting of outer layers of a flexible, tightly woven fabric and an inner layer consisting of a material designed to filter out particles. We calculated that the particle size most likely to deposit in the respiratory tract when wearing a mask is ∼2 μm.
Discrepancies between material filtration efficiency and inward/outward protection efficiency indicated that the fit of the mask was important. Inward protection efficiency and outward protection efficiency were similar for many masks the two efficiencies diverged for stiffer materials and those worn more loosely (e.g., bandana) or more tightly (e.g., wrapped around the head) compared to a standard earloop mask. The thin acrylic and face shield performed worst. The vacuum bag performed best, with efficiencies of 54-96% for all three metrics, depending on particle size. However, these efficiencies increased rapidly with particle size, and many materials had efficiencies >50% at 2 μm and >75% at 5 μm.
At the most penetrating particle size, the vacuum bag, microfiber cloth, and surgical mask had material filtration efficiencies >50%, while the other materials had much lower filtration efficiencies. We evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin.
0 kommentar(er)
