Fit testing looks like an unmet need for surgical and improvised face masks. If air can leak around the sides, it doesn’t matter how good the material is, and earloop masks look particularly bad along these lines.
https://totobobo.com/blog/category/fit-test/ illustrates a quantitative fit test for respirators that form excellent if not perfect seals around the nose and mouth. (“Below is a 9 minutes video showing the entire process of a Quantitative fit test. The final result shows the Totobobo mask with a pair of F96 filters is able to reduce ambient particles by 142 times.) It uses a TSI Portacount instrument which appears to require a sampling port in the respirator itself (probably not as easy to do with a surgical or cloth face mask) but this underscores the proposition that almost all the masks now in use offer far less protection than they should simply due to the leakage issue.
I have not been able to find an ASTM standard (or other standard) for face mask (as opposed to respirator) fit testing. If anybody knows of one, please let me know at theboss “at” ct-yankee.com.
In the mean time, a superior seal ought to be a selling point for all face masks. It doesn’t matter if you have an ASTM Level 2 surgical mask or other superior material; if a contagious aerosol can get in around the edges, it doesn’t matter what the mask is made from. This looks like a huge (and easily correctable) gap in the protection available from the masks now in circulation.