Yesterday, I read some paper from 2010 which found near identical filtration results for one type of N95 mask vs. 2 types of N99 mask... Basically none of these

Yesterday, I read some paper from 2010 which found near identical filtration results for one type of N95 mask vs. 2 types of N99 mask... Basically none of these masks will filter all the particles, hence healthcare worker will eventually infect themselves unless you go full warzone (e.g. hazmat suites for everyone). All of this stuff is about managing risk (as is running around with simple masks and social distancing).