During a pandemic in which aerosol and droplet transmission is possible, the demand for masks that meet medical or workplace standards can prevent most individuals or organizations from obtaining suitable protection. Cloth masks are widely believed to impede droplet and aerosol transmission but most are constructed from materials with unknown filtration efficiency, airflow resistance and water resistance. Further, there has been no clear guidance on the most important performance metrics for the materials used by the general public (as opposed to high-risk healthcare settings). Here we provide data on a range of common fabrics that might be used to construct masks. None of the materials were suitable for masks meeting the N95 NIOSH standard, but many could provide useful filtration (>90%) of 3 micron particles (a plausible challenge size for human generated aerosols), with low pressure drop. These were: nonwoven sterile wraps, dried baby wipes and some double-knit cotton materials. Decontamination of N95 masks using isopropyl alcohol produces the expected increase in particle penetration, but for 3 micron particles, filtration efficiency is still well above 95%. Tightly woven thin fabrics, despite having the visual appearance of a good particle barrier, had remarkably low filtration efficiency and high pressure drop. These differences in filtration performance can be partly explained by the material structure; the better structures expose individual fibers to the flow while the poor materials may have small fundamental fibers but these are in tightly bundled yarns. The fit and use of the whole mask are critical factors not addressed in this work. Despite the complexity of the design of a very good mask, it is clear that for the larger aerosol particles, any mask will provide substantial protection to the wearer and those around them.

中文翻译：

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用于临时面具的材料特性

在可能发生气溶胶和飞沫传播的大流行期间，对符合医疗或工作场所标准的口罩的需求可能会阻止大多数个人或组织获得适当的保护。人们普遍认为布口罩会阻碍飞沫和气溶胶的传播，但大多数是由过滤效率、气流阻力和防水性能未知的材料制成的。此外，对于公众使用的材料（与高风险医疗机构相反）的最重要性能指标，没有明确的指导。在这里，我们提供了一系列可用于制作口罩的常见织物的数据。没有一种材料适用于符合 N95 NIOSH 标准的口罩，但许多材料可以提供有用的过滤 (> 90%) 的 3 微米颗粒（对于人类产生的气溶胶来说，这是一个合理的挑战尺寸），具有低压降。它们是：无纺布无菌包裹物、干婴儿湿巾和一些双面针织棉材料。使用异丙醇对 N95 口罩进行净化会产生预期的颗粒渗透增加，但对于 3 微米颗粒，过滤效率仍远高于 95%。紧密编织的薄织物，尽管具有良好的颗粒屏障的视觉外观，但过滤效率和压降非常低。这些过滤性能的差异可以部分由材料结构来解释；较好的结构将单根纤维暴露在流动中，而较差的材料可能具有较小的基本纤维，但它们是紧密捆绑的纱线。整个面罩的适合和使用是这项工作中未涉及的关键因素。尽管非常好的口罩设计很复杂，但很明显，对于较大的气溶胶颗粒，任何口罩都会为佩戴者及其周围的人提供实质性的保护。