A face mask cannot possibly stop a coronavirus.
Size of the Coronavirus
According to a study published in the New England Journal of Medicine https://www.nejm.org/doi/10.1056/NEJMoa2001017
“Electron micrographs of negative-stained 2019-nCoV particles were generally spherical with some pleomorphism. Diameter varied from about 60 to 140 nm. Virus particles had quite distinctive spikes, about 9 to 12 nm, and gave virions the appearance of a solar corona.”
A nanometer is one-thousandths of a micrometer (mm, also called micron). A virus diameter of 60 to 140 nanometers is a diameter of 0.060 to 0.140 micrometer.
Filter capability of N95 surgical mask
A N95 Surgical Mask is a mask manufactured to meet the NIOSH part 84 regulation N95. This government regulation requires the mask to filter out 95% of particles that are larger than 0.3 micrometers (0.300 microns). It will let through 5% of particles greater than 0.300 microns.
In other words, N95 mask will NOT filter out five side-by-side coronavirus, Nor 5% of larger particles that it is not required to filter out. Plus whatever gets in around the mask — and this is for government regulated surgical masks, not for cloth masks.
Cloth masks are just for virtue signaling politicians.
You may also be interested in my post that proves Asymptomatic coronavirus carriers have ZERO risk of spreading the virus.