Ummmmmmm, most buildings are a "completely enclosed environment". The Massachusetts study, not in a prison, actually came in at 74%, higher than the prison study. Not sure what you mean by air filtration. Do most buildings have signs up saying they have "air filtration"? Come on now, most building do not have adequate "air filtration". The types of masks that most people wear are only 10% effective. In case you are lacking in math skills, that means that the type of masks most people wear don't work 90% of the time, that is according to the CDC. The CDC also says that social distancing outside is not necessary most of the time and that social distancing inside is close to worthless because most buildings do not have proper "air filtration" and the aerosols spread throughout the building.