This work demonstrates the qualitative fluid flow characteristics of a standard N95 respirator with and without an exhalation valve. Schlieren imaging was used to compare an adult male breathing through an N95 respirator with and without a valve. The schlieren imaging technique showed the flow of warm air passing through these respirators but did not provide information about droplet penetration. For this, strategic lighting of fog droplets was used with a mannequin head to visualize the penetration of droplets through both masks. The mannequin exhaled with a realistic flow rate and velocity that matched an adult male. The penetration of fog droplets was also visualized with a custom system that seals each respirator onto the end of a flow tube. Results of these qualitative experiments show that an N95 respirator without an exhalation valve is effective at blocking most droplets from penetrating through the mask material. Results also suggest that N95 respirators with exhalation valves are not appropriate as a source control strategy for reducing the proliferation of infectious diseases that spread via respiratory droplets.

中文翻译：

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使用纹影成像和光散射对带和不带呼气阀的 N95 呼吸器进行流量可视化

这项工作展示了带有和不带有呼气阀的标准 N95 呼吸器的定性流体流动特性。纹影成像用于比较一名成年男性通过带阀门和不带阀门的 N95 呼吸器呼吸。纹影成像技术显示了通过这些呼吸器的热空气流，但没有提供有关飞沫渗透的信息。为此，雾滴的战略照明与人体模型头部一起使用，以可视化液滴通过两个面罩的渗透。人体模型以与成年男性相匹配的逼真的流速和速度呼气。雾滴的渗透也可以通过定制系统进行可视化，该系统将每个呼吸器密封在流量管的末端。这些定性实验的结果表明，不带呼气阀的 N95 呼吸器可有效阻止大多数飞沫穿透面罩材料。结果还表明，带呼气阀的 N95 呼吸器不适合作为减少通过呼吸道飞沫传播的传染病扩散的源头控制策略。