Evaluating total outward leakage of face-worn products across various particle sizes for source control against submicron aerosols: Implications for public health protection

Abstract

During COVID-19, the general public widely used face-worn products (FwPs) to mitigate viruses spread via airborne transmission. This study investigated the effectiveness of various FwP categories in reducing submicron aerosol transmission by evaluating total outward leakage (TOL) across particle sizes. Nine FwP categories were tested: ASTM F2100 Levels 1, 2, and 3 masks (categories 1–3); single-layer cloth mask (category 4); cloth masks with pockets, tested with and without HEPA and PM 2.5 filters insert (categories 5–8); and three-layer disposable masks (category 9). The TOL of these FwPs was assessed over multiple donnings on medium and large artificial headforms, and TOL mean diameter (TOLMD) was calculated. Results showed that cloth FwPs (categories 4–8) had higher TOL and a steeper increase with particle size (20–210 nm) compared to ASTM-compliant FwPs (categories 1–3) and disposable masks (category 9). Categories 4, 6, and 7 exhibited TOL values up to 60 % for particles >100 nm, which are significant for viral transmission. Non-ASTM-compliant products exhibited higher TOL for larger submicron particles. The analysis of TOLMD suggested that multiple donnings impact TOL across particle sizes. The findings established a link between TOL and particle size, providing more detailed guidance for the public in selecting FwPs for source control. This study also highlighted the importance of further research into the reusability of FwPs to inform public health recommendations for respiratory protection.