A rapid assessment of the efficacy of commonly used mask making fabrics to block respiratory droplets

Due to the COVID-19 pandemic, many people now use cloth masks of various fabrics to protect against the spread of viral disease. We developed a simple and accessible method to test which fabrics block the greatest mass percent of simulated respiratory droplets. Single-layer fabric samples of polyester, silk, linen, cotton, and polypropylene were tested using a commercially available and cost-effective spray bottle that produced droplets similar in size distribution to human respiratory droplets. The cotton fabric was the most efficient, blocking a median of 79% of simulated respiratory droplets. The polyester fabric was close behind with a median of 75% of droplets being blocked, greater than fabrics made of silk, linen, or polypropylene. The polyester and cotton fabrics both blocked significantly more droplets than the silk fabric, and there was a non-significant trend for the cotton and polyester fabrics to block more droplets than samples made of other fabrics. We measured droplet sizes produced by the spray bottle passing through each fabric by using silicone oil to capture the passed droplets for microscopic analysis. The polyester fabric allowed the least mass of droplets to pass through. The fabrics made from polyester, cotton, and silk blocked nearly all droplets above 100 µm in diameter, while the fabrics made from polypropylene and linen allowed a substantial number of large droplets to pass through. These data suggest that polyester and cotton are the most effective mask materials of the five fabrics tested. These methods can be rapidly and inexpensively deployed to test potential mask fabrics to make more effective masks to help stop the spread of COVID-19 or other respiratory diseases.