Filtration efficiency and breathability of fabric masks and their dependence on fabric characteristics
Date
2022
Authors
Fontenot, Jacob, author
Volckens, John, advisor
Carter, Ellison, committee member
Jathar, Shantanu, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Throughout the COVID-19 pandemic, the demand for face coverings offering two-way protection significantly increased, which resulted in widespread use of masks made from common fabrics (e.g., wool, cotton, and synthetic materials). However, the effectiveness of these fabric masks, which vary in material and design, is not well understood. This work investigates the performance of fabric masks, namely filtration efficiency and breathability, and their dependence on fabric characteristics. Filtration efficiency (FE) and flow resistance – a measure of mask breathability – were evaluated for 50 fabric masks, followed by individual layer testing (n = 70 total layers). The characteristics of the fabric layers, namely yarn diameter, fiber diameter, thread count, air permeability, porosity, cloth cover factor, infra-red (IR) attenuation, and fabric thickness were quantified in a laboratory setting. Fabric mask FEs were relatively low (i.e., < 50%) for submicron particles but increased with particle diameter. Approximately half of the masks achieved a FE meeting the Level 1 barrier standard specified in ASTM F3502-21. The FE and flow resistance of the component fabric layers was found to accurately predict the FE and flow resistance of the entire mask; therefore, we find that fabric masks can generally be treated as filters in series. FE exhibited the strongest relationship with cloth cover factor, IR attenuation, air permeability, and the number of fabric layers; in contrast, we found little to no relationship between FE and yarn diameter, fiber diameter, thread count, porosity, fabric thickness, and fabric material (e.g., natural vs. synthetic). Results of this work should help inform the design of more effective fabric masks, which could prove especially useful for airborne infectious disease response efforts in resource limited environments (i.e., where N95 technologies are not available) around the planet.