Beyond inhalation protection: Assessing cloth mask effectiveness as source control devices

This study investigates the effectiveness of cloth masks as source control devices during violent respiratory events such as coughing and sneezing. Utilizing a novel experimental platform integrating a mechanical cough simulator and high-speed laser visualization, we quantitatively assess the filtration efficiency of various cloth mask materials. Our results reveal significant variability in the cumulative escaped droplet volume across different fabrics, challenging the assumption that fabrics with similar porosity yield comparable performance. We introduce the concept of active porosity, highlighting its critical role in mask performance for source control, and demonstrate that masks with lower active porosity more effectively mitigate droplet transmission. Furthermore, our findings suggest that a mask's performance in inhalation protection does not directly correlate with its efficacy in source control, emphasizing the need for tailored testing standards. The study also explores the impact of water content on mask performance, revealing that moisture accumulation can significantly alter the filtration efficiency and pressure dynamics of the mask, potentially compromising its protective seal. These insights provide a foundation for improving cloth mask design and standards to better address the challenges of airborne transmission during pandemics.