It bothered me to see all those videos and claims online about face masks containing harmful particles so I decided to fact check this for myself. Bought a cheap USB-microscope and zoomed in on this one face mask I was handed in an event but which I never used. In a few seconds I started to discover these black "worms" that seem to activate when breathing on them gently. Also tried to poke it with a toothpick...

I don't know what these are but they are there and common sense says they don't belong in face masks or in your lungs -so watch out!