NIST Mask Analysis
Recent studies demonstrate that cotton fabrics tend to perform better than synthetics for general public use. Cotton flannels were especially effective. As part of this research, Edward Vicenzi used a scanning electron microscope to study the fabrics. His images gave scientists important insights into the particle-filtering properties of different fabrics.
Cotton may be best for the fabric masks that the general public wears, but medical-grade masks require more stringent standards. Surgical masks contain filtering material made by melting and then air-blowing polypropylene into a web. The fibers are smaller with greater surface area than cotton fibers, which is one reason this polypropylene is an especially effective filtering material.
N95 respirators are named as such because they filter out 95% of particles that are 0.3 millionths of a meter in size. N95 is a well-known successful filtration product for medical grade masks. NIST scientists are still studying the filtration properties of mask fabrics to continue understanding how to keep the general public safe from COVID-19 or whatever might arise in the future.