HEPA filter improves homemade cloth mask to surgical mask standards

During the COVID-19 pandemic, many people turned to homemade cloth masks, which are often cheaper and more comfortable than surgical and N95 masks. While surgical and N95 masks are more effective at preventing droplets from seeping through the mask, they do not fit every individual properly and can cause facial eczema for those that have latex allergies.

Hoping to improve homemade cloth mask efficacy, Narayan et al. studied the use of a high-efficiency particulate air, or HEPA, filter inside such masks. The researchers tested double-layered cloth masks with and without HEPA filters in between the layers to see if HEPA filters could block respiratory droplets from making it through the mask.

Their results showed that the highly hydrophobic nature of the HEPA filter prevented water droplets from making it through the mask, even when droplets were applied at higher velocities to simulate coughing. Additional breathability tests showed that airflow speeds through the filtered cloth masks resembled surgical mask speeds.

“The filter both stops the generation of the secondary droplets on the rear side and inhibits capillary seeping that could contaminate the rear-side surface with infectious liquid,” said author Rajneesh Bhardwaj. “Thus, our proposed design elevates the performance of homemade cloth masks to that of commercially available surgical masks.”

The authors are excited by the efficacy of the HEPA filter layer in cloth masks and are looking to study other hydrophobic porous materials that could be used in place of HEPA filters.

Source: “Assessing effectiveness and comfortability of a two-layer cloth mask with a high-efficiency particulate air (HEPA) insert to mitigate COVID-19 transmission,” by Yagya Narayan, Sanghamitro Chatterjee, Amit Agrawal, and Rajneesh Bhardwaj, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0094116 .

This paper is part of the Flow and the Virus Collection, learn more here .