I'm required to wear a mask and/or shield for work...normally I wear my shield outside at recess. The one day this week, I chose to wore my mask. I was playing tag with the kiddos and holy cow, I could not breathe. I had to stand way far back from anybody and take the mask off for a moment just to get fresh air. The masks certainly do block molecules (at least some) from traveling through! I think I'll continue primarily using the shield...although on the colder days we have gone out, the second I step outside it becomes a fogged up mess. I need some windshield wipers attached to it.