Abstract

Homemade cloth masks and other improvised face coverings have become widespread during the COVID-19 pandemic driven by severe shortages of personal protective equipment. In this study, various alternative (mostly common household) materials, which have not traditionally been used in respiratory protective devices, were tested for particle filtration performance and breathability. Most of these materials were found of some—but rather limited—utility in facemasks. At a breathing flow rate of 30 L min⁻¹, 17 out of 19 tested materials demonstrated collection efficiency below 50%; at 85 L min⁻¹, only one material featured particle collection efficiency above 50%. Pressure drop values were mostly below 4 mm w.g. (observed in 89% of cases for the two flow rates), which provides comfortable breathing. Only for one fabric material (silk) tested at 85 L min⁻¹ did the pressure drop reach 11 mm w.g. Based on these results, a three-layer facemask prototype was designed and fabricated comprised of the best performing materials. Additional tests were conducted to examine possible particle detachment/shedding from the materials used in the newly developed facemask, but no such phenomenon was observed. The prototype was evaluated on 10 human subjects using the standard OSHA-approved quantitative fit testing protocol. The mask protection level, determined as an adopted fit factor, was found to lie between that of the two commercial surgical/medical masks tested for comparison. A 10-cycle washing of the mask prototype lowered its collection efficiency across the particle size range; however, washing did not substantially affect mask breathability. The study revealed that although homemade masks offer a certain level of protection to a wearer, one should not expect them to provide the same respiratory protection as high-end commercial surgical/medical masks or—by any means—NIOSH-certified N95 filtering facepieces.

 抽象的

在 COVID-19 大流行期间，由于个人防护设备严重短缺，自制布口罩和其他简易面罩已变得普遍。在这项研究中，对传统上未用于呼吸防护装置的各种替代材料（主要是常见的家用材料）进行了颗粒过滤性能和透气性测试。大多数这些材料在口罩中都有一定的用途，但用途相当有限。在呼吸流速为 30 L min ^-1时，19 种测试材料中有 17 种的收集效率低于 50%；在 85 L min ⁻¹下，只有一种材料的颗粒收集效率高于 50%。压降值大多低于 4 毫米水柱（两种流速下 89% 的情况下观察到），这提供了舒适的呼吸。只有一种织物材料（丝绸）在 85 L min ^-1下测试时压降达到 11 mm wg 根据这些结果，设计并制造了由性能最佳的材料组成的三层面罩原型。还进行了额外的测试来检查新开发的面罩所用材料是否可能存在颗粒脱落/脱落，但没有观察到这种现象。使用 OSHA 批准的标准定量拟合测试协议对 10 名受试者进行了原型评估。面罩的防护等级被确定为采用的贴合系数，被发现位于用于比较测试的两种商用外科/医用面罩的防护等级之间。面罩原型的 10 次循环清洗降低了其在整个颗粒尺寸范围内的收集效率；然而，洗涤并没有显着影响面罩的透气性。 研究表明，虽然自制口罩可以为佩戴者提供一定程度的保护，但人们不应期望它们能够提供与高端商用外科/医用口罩或（无论如何）NIOSH 认证的 N95 过滤面罩相同的呼吸保护。