This is how diseases is spread. https://www.youtube.com/watch?v=MeCGTRh27Tg It is not from you projectile spitting in someone's face while talking to them. It is simply your breath. An aerosol gas leeching around. Imagine a grocery store with hundreds of people in it. It is a literal stew of everyone's breath swirling around. You have to stop the moisture breath from getting out to prevent disease spread.
It's not protecting you from getting it. It's protecting others from you spreading it.
This is how diseases is spread. https://www.youtube.com/watch?v=MeCGTRh27Tg It is not from you projectile spitting in someone's face while talking to them. It is simply your breath. An aerosol gas leeching around. Imagine a grocery store with hundreds of people in it. It is a literal stew of everyone's breath swirling around. You have to stop the moisture breath from getting out to prevent disease spread.