Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA.
VA Puget Sound Health Care System, Seattle, WA.
J Occup Environ Hyg. 2021 Jun;18(6):265-275. doi: 10.1080/15459624.2021.1913283. Epub 2021 May 14.
The COVID-19 pandemic has caused a high demand for respiratory protection among health care workers in hospitals, especially surgical N95 filtering facepiece respirators (FFRs). To aid in alleviating that demand, a survey of commercially available filter media was conducted to determine whether any could serve as a substitute for an N95 FFR while held in a 3D-printed mask (Stopgap Surgical Face Mask from the NIH 3D Print Exchange). Fourteen filter media types and eight combinations were evaluated for filtration efficiency, breathing resistance (pressure drop), and liquid penetration. Additional testing was conducted to evaluate two filter media disinfection methods in the event that the filters were reused in a hospital setting. Efficiency testing was conducted in accordance with the procedures established for approving an N95 FFR. One apparatus used a filter-holding device and another apparatus employed a manikin head to which the 3D-printed mask could be sealed. The filter media and combinations exhibited collection efficiencies varied between 3.9% and 98.8% when tested with a face velocity comparable to that of a standard N95 FFR at the 85 L min used in the approval procedure. Breathing resistance varied between 10.8 to >637 Pa (1.1 to > 65 mm HO). When applied to the 3D-printed mask efficiency decreased by an average of 13% and breathing resistance increased 4-fold as a result of the smaller surface area of the filter media when held in that mask compared to that of an N95 FFR. Disinfection by dry heat, even after 25 cycles, did not significantly affect filter efficiency and reduced viral infectivity by > 99.9%. However, 10 cycles of 59% vaporized HO significantly (p < 0.001) reduced filter efficiency of the media tested. Several commercially available filter media were found to be potential replacements for the media used to construct the typical cup-like N95 FFR. However, their use in the 3D-printed mask demonstrated reduced efficiency and increased breathing resistance at 85 L min.
COVID-19 大流行导致医院医护人员对呼吸防护的需求很高，特别是外科用 N95 过滤式面罩（FFR）。为了缓解这种需求，对市售过滤介质进行了调查，以确定在 3D 打印面罩（NIH 3D 打印交换中的临时外科面罩）中使用时，是否有任何过滤介质可以替代 N95 FFR。评估了 14 种过滤介质类型和 8 种组合的过滤效率、呼吸阻力（压降）和液体渗透。进行了额外的测试，以评估两种过滤介质的消毒方法，如果在医院环境中重复使用过滤器。效率测试是按照批准 N95 FFR 的程序进行的。一种装置使用过滤器保持装置，另一种装置使用可以密封 3D 打印面罩的人头模型。当以类似于标准 N95 FFR 的面速（在批准程序中使用的 85 L min）进行测试时，过滤介质和组合的收集效率在 3.9%至 98.8%之间变化。呼吸阻力在 10.8 至> 637 Pa（1.1 至> 65 mm HO）之间变化。当应用于 3D 打印面罩时，由于过滤介质在该面罩中的表面积比 N95 FFR 小，效率平均降低 13%，呼吸阻力增加 4 倍。即使经过 25 次循环，干热消毒也不会显著影响过滤效率，并将病毒感染力降低> 99.9%。然而，10 次 59%汽化 HO 的循环会显著（p < 0.001）降低测试介质的过滤效率。发现几种市售过滤介质可能是典型杯状 N95 FFR 所用介质的替代品。然而，它们在 3D 打印面罩中的使用表明，在 85 L min 时，效率降低，呼吸阻力增加。
