What to Wear: The Filtration Performance of Alternative Materials Used to Construct Do-It-Yourself Masks

ABSTRACT

The COVID-19 pandemic has shown that much of the world, including the United States, is ill-prepared for the material demands of a global crisis. In response to this shortage of Personal Protective Equipment (PPE), we have conducted filtration efficiency and pressure drop testing of a range of common materials used for constructing do-it-yourself masks, including an allergen filter, a vacuum bag, a heavy-duty tool wipe, and a standard cotton bandana, as well as a standard 3-ply surgical mask, a medical drape and an industrially available composite filter material. Size-resolved percent penetration of each material by particles with diameters ranging from 25 to 500 nm was measured at three face velocities (0.72 cm s^-1, 4.30 cm s^-1, 13.0 cm s^-1). The allergen filter performed best, only allowing the penetration of 5% ± 3% of the 300 nm particles through the material at a face velocity of 13.0 cm s^-1, comparable to human breathing during heavy physical work. In comparison, the surgical mask and the cotton bandana allowed 39 ± 1% and 51% ± 1% of the 300 nm particles to pass through at the same face velocity, respectively. According to the calculated filter quality, the best choices for mask construction are the allergen filter, industrial composite filter, and the vacuum bag. Structure and morphology of the materials were characterized by scanning electron microscopy (SEM), image analysis, and thickness measurements to investigate physical characteristics which improve filtration. This study shows that certain household and commercially available materials and combinations can be used in the construction of highly effective face masks.