Can clothe masks be a substitute for N95 masks?
The researchers at the University of Chicago performed a study to check the purification ability of the cloth masks. They made masks by joining one layer of tightly woven cotton sheet1 and two layers of polyester-spandex chiffon2, which is a fabric commonly used in evening gowns. These masks filtered out 80% to 90% spray particles ranging from 10 nanometres to 6 micrometres in diameter at normal human respiratory flow rate and volume.
This performance was close to N95 mask materials. Comparable results were obtained when natural silk or flannel or cotton quilt with cotton polyester batting were substituted for the chiffon.
By this experiment, the researchers showed that tightly woven fabric such as cotton can act as a mechanical barrier to spray particles, where the fabrics that hold a static charge like certain types of chiffon and natural silk serve as an electrostatic barrier. The researchers cautioned, however, that even 1% gap reduces the filtering efficiency of all masks by half or more. This fact emphasizes the proper fitting of a mask to the face.
The author concludes that for an average person, a cloth mask which has been made carefully is sufficient to protect from common diseases that are transmitted by aerosols or dew. An average person should always use cloth mask while going out of home. A mask made up of cloth will be economical to the pocket and preserve the national resources for more specific needs.