Abstract

Universal mask wearing is recommended to help control the spread of COVID-19. Masks reduce the expulsion of aerosols of respiratory fluids into the environment (called source control) and offer some protection to the wearer. Masks are often characterized using filtration efficiency, airflow resistance, and manikin or human fit factors, which are standard metrics used for personal protective devices. However, none of these metrics are direct measurements of how effectively a mask blocks coughed and exhaled aerosols. We studied the source control performance of 15 cloth masks (face masks, neck gaiters, and bandanas), two medical masks, and two N95 filtering facepiece respirators by measuring their ability to block aerosols ≤7 µm expelled during simulated coughing and exhalation (called source control collection efficiency). These measurements were compared with filtration efficiencies, airflow resistances, and fit factors measured on manikin headforms and humans. Collection efficiencies for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. Filtration efficiencies for the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on headforms and 1.0 to 4.0 on human subjects. The Spearman’s rank correlation coefficients between the source control collection efficiencies and the standard metrics ranged from 0.03 to 0.68 and were significant in all but two cases. However, none of the standard metrics were strongly correlated with source control performance. A better understanding of the relationships between source control collection efficiency, filtration efficiency, airflow resistance, and fit factor is needed.

摘要

建议佩戴通用口罩以帮助控制 COVID-19 的传播。口罩可减少呼吸液气溶胶向环境中的排放（称为源头控制），并为佩戴者提供一些保护。口罩通常使用过滤效率、气流阻力和人体模型或人体适合因素来表征，这些是用于个人防护设备的标准指标。然而，这些指标都不是直接衡量口罩阻挡咳嗽和呼出气溶胶的效果。我们研究了 15 个布制口罩（面罩、护颈器和头巾）、两个医用口罩和两个 N95 过滤面罩呼吸器的源头控制性能，方法是测量它们在模拟咳嗽和呼气期间阻挡 ≤7 µm 的气溶胶（称为源头）的能力控制收集效率）。将这些测量结果与在人体模型头型和人体上测量的过滤效率、气流阻力和贴合系数进行了比较。布口罩的收集效率在咳嗽时为 17% 至 71%，呼气时为 35% 至 66%。布口罩的过滤效率从 1.4% 到 98% 不等，而头模的贴合系数为 1.3 到 7.4，人体受试者的贴合系数为 1.0 到 4.0。源代码控制收集效率和标准指标之间的 Spearman 等级相关系数范围为 0.03 到 0.68，并且在除两个案例之外的所有案例中均显着。然而，没有一个标准指标与源代码控制性能密切相关。需要更好地理解源头控制收集效率、过滤效率、气流阻力和适合系数之间的关系。