Which Face Masks Are Most Protective?

Twenty commonly available fabrics and materials were evaluated by researchers from the University of Cambridge and Northwestern University, for their ability to reduce air concentrations of ultrafine particles at coughing face velocities. A 3M N95 mask and hospital-grade surgical mask were tested for the sake of comparison.

Two types of vacuum bag, a disposable HEPA vacuum bag, and a washable HEPA vacuum bag, were evaluated due to the number of people attempting to use these materials as face mask filters. Eighteen fabrics were also tested as a single layer. Lastly, fabrics were layered to represent potential mask designs.

This study's results published on September 22, 2020, found 'when fabrics were layered, a higher percentage of ultrafine particles were filtered.'

The average filtration efficiency of single layer fabrics and of the layered combination was found to be 35% and 45%, respectively. Non-woven fusible interfacing, when combined with other fabrics, could add up to 11% additional filtration efficiency.