This is an outstanding article on masks and computer models: https://www.vanityfair.com/news/2020...jvK9HyLAV4ZjtE

"On the screen-share, De Kai first ran a simulation that shows what happens when COVID-19 strikes a population in which no one wears a mask. The orange and red dots proliferate at a frightening speed; “susceptibles” becoming “exposed/infected,” then recovered or dead. “This is what you don’t want,” said De Kai. He changed the setting to simulate what would happen if 100% of the make-believe population wore masks; almost all of the dots would stay blue—with each of them surrounded by a white square, representing someone wearing a mask."