Dr. Christine Eady MannVerified account

This is a real phenomenon.https://twitter.com/ballerinaX/status/1246276118174302216 …

Yes, I think that's the danger.

And just poor mask hygiene. People tug on 'em take 'em off and on, touch their face adjusting them. Wear valved masks that would just make a virus concentrate spray spout. It takes some training of a sort.

I also read that breathing with the mask on makes the tiny holes in it bigger. The longer you wear it the bigger they get.

Depends on the mask material, design & purpose. There are many for different things, particles, virus, VOCs Oily vapors etc... It's a bit involved which is why it's such a lively scene.