Non-woven materials for cloth-based face masks inserts: relationship between material properties and sub-micron aerosol filtration

Current guidance by leading public health agencies recommends wearing a 3-layer cloth-based face mask with a middle non-woven material insert to reduce the transmission of infectious respiratory viruses like SARS-CoV-2. In this work we explore the material characteristics for a range of readily available non-woven materials and their sub-micron particle filtration efficiency (PFE), with the aim of providing evidence-based guidelines for selecting appropriate materials as inserts in cloth-based masks. We observed a wide range of ideal PFE for the tested non-woven materials, with polypropylene, Swiffer and rayon/polyester blend providing the highest PFE and breathability. Our results suggest that materials comprising loose 3D fibrous webs ( e.g. flannel, Swiffer and gauze) exhibited enhanced filtration efficiency compared to compressed counterparts. Common modifications to fabrics, such as water-resistant treatment and a sewn seam were also investigated. Overall, we demonstrate that adding an appropriate non-woven material as an insert filter can significantly improve the performance of cloth-based masks, and there exist suitable cellulose-based alternatives to polypropylene. Sub-micron aerosol filtration of non-woven materials and fabric treatments were investigated. Select low-cost, readily available and easily cut non-woven materials were identified as suitable filter inserts for cloth-based masks.