Abstract As a consequence of the COVID-19 pandemic caused by the SARS-CoV-2 virus, the widespread daily use of face masks is promoted worldwide. Particle-size dependent filtration efficiencies (FE; dp = 30 nm–10 µm), applying a particle counting approach, and additionally pressure drops (Δp) were determined for 44 samples of household materials and several medical masks. Huge FE differences were found between sample materials and for different particle sizes, spanning from <10% up to almost 100%. Minimum FE were determined for dp = 50–500 nm particles with significantly larger values for dp = 30 nm particles and especially for those with dp > 2.5 µm. Measurements at different numbers of layers showed that stacks of textiles can be treated as separate filters and total FE and Δp can readily be estimated from the features of the individual layers, leaving laborious measurements of individual combinations obsolete. For many materials, electrostatic attraction contributes strongly to overall FE for particles up to 100 nm diameter. Measurements with defined leaks showed that already a small fractional leak area of 1–2% can strongly deteriorate total FE. This is especially the case for particles smaller than 5 µm diameter, where FE dropped by 50% or even two thirds. Our measurements show that by stacking an adequate number of layers of many fabrics, decent filtration efficiencies can be reached for homemade face masks over large particle size ranges with acceptable pressure drop across the material. Very important, however, is good fit of the masks to minimize leak flows and selection of non-hazardous mask material.

中文翻译：

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自制口罩家用材料的气溶胶过滤效率：材料特性、粒径、粒子电荷、面速度和泄漏的影响

摘要 由于 SARS-CoV-2 病毒引起的 COVID-19 大流行，全球范围内广泛推广了口罩的日常使用。应用颗粒计数方法，测定了 44 个家用材料样品和几个医用口罩的粒径相关过滤效率 (FE；dp = 30 nm–10 µm) 和压降 (Δp)。在样品材料和不同粒径之间发现了巨大的 FE 差异，范围从 <10% 到几乎 100%。最小 FE 是为 dp = 50-500 nm 颗粒确定的，dp = 30 nm 颗粒的值明显更大，尤其是那些 dp > 2.5 µm 的颗粒。不同层数的测量表明，成堆的纺织品可以被视为单独的过滤器，总 FE 和 Δp 可以很容易地从各个层的特征中估计出来，从而使对各个组合的费力测量过时了。对于许多材料，静电引力对直径达 100 nm 的颗粒的整体 FE 贡献很大。对确定泄漏的测量表明，1-2% 的小部分泄漏区域已经可以使总 FE 严重恶化。对于直径小于 5 µm 的颗粒尤其如此，其中 FE 下降了 50% 甚至三分之二。我们的测量表明，通过堆叠足够数量的许多织物层，自制口罩可以在大粒径范围内达到不错的过滤效率，同时材料上的压降也可以接受。