[ConservativeInPA]

They do not work in theory, nor practice. In simple terms, the virus is small enough to penetrate the fabric of a mask. That’s the theory. The practice obviously has proved itself as wanting.

[2aProtectsTheRest]

"In simple terms, the virus is small enough to penetrate the fabric of a mask. That’s the theory."

Virus proteins rapidly denature in open air. They can only survive within water droplets. SARS-CoV-2 primarily transmits via respiratory droplets, which are readily filtered by even basic masks. Here's a visual of that happening from a study conducted:

Source

SARS-CoV-2 requires droplets in order to travel between persons. A properly made, properly worn mask reduces both the volume and the range of those droplets.

In practice, many people wear poorly constructed masks and many wear masks incorrectly. That isn't a problem with the masks; it's an education problem.

[excalibur21]

They do not work in theory, nor practice. In simple terms, the virus is small enough to penetrate the fabric of a mask.

COVID-19 is about .12 microns in size. It’s my understanding that trying to stop it with a common mask is like shooting a BB through a chain link fence.