Abstract

Strong evidence exists indicating that aerosol transmission of the novel coronavirus SARS-CoV-2 is a significant transmission modality. We experimentally evaluated the impact of ventilation on aerosol dynamics and distribution along with the effective filtration efficiency (EFE) of four different mask types, with and without mask fitters, in a classroom setting. These were used to estimate aerosol conditional infection probability using the Wells–Riley model for three scenarios with different ventilation and mask interventions. Aerosol measurements confirmed that aerosol in the room was uniform within a factor of 2 for distances >2 m from the source. Mask EFE results demonstrate that most masks fit poorly with estimated leakage rates typically >50%. However, EFEs approaching the mask material FE were achievable using mask fitters. Infection probability estimates indicate that ventilation alone is not able to achieve probabilities <0.01 (1%). The use of moderate to high EFE masks reduces infection probability, >5× in some cases. Reductions provided by ventilation and masks are synergistic and multiplicative. The results reinforce the use of properly donned masks to achieve reduced aerosol transmission of SARS-CoV-2 and other infectious diseases and motivate improvements in the EFE of masks through improved design or use of mask fitters.

摘要

有强有力的证据表明，新型冠状病毒 SARS-CoV-2 的气溶胶传播是一种重要的传播方式。我们在课堂环境中通过实验评估了通风对气溶胶动力学和分布的影响，以及四种不同面罩类型的有效过滤效率 (EFE)，有和没有面罩装配工。这些用于使用 Wells-Riley 模型估计气溶胶条件感染概率，用于具有不同通风和面罩干预的三种情况。气溶胶测量证实，对于距源 >2 m 的距离，房间中的气溶胶在 2 倍以内是均匀的。面罩 EFE 结果表明，大多数面罩不适合，估计泄漏率通常 >50%。然而，使用掩模装配工可以实现接近掩模材料 FE 的 EFE。感染概率估计表明，仅靠通风无法达到 <0.01 (1%) 的概率。使用中到高 EFE 口罩可降低感染概率，在某些情况下 >5 倍。通风和面罩提供的减少是协同和乘法的。结果加强了正确佩戴口罩的使用，以减少 SARS-CoV-2 和其他传染病的气溶胶传播，并通过改进设计或使用口罩钳工来促进口罩 EFE 的改进。