So what happens if we put air purifiers with HEPA filter (1) indoors then? Has anyone measured this? (1) HEPA filters have good filtration efficiency even at p

So what happens if we put air purifiers with HEPA filter (1) indoors then? Has anyone measured this? (1) HEPA filters have good filtration efficiency even at particle sizes smaller than MPPS https://www.sciencedirect.com/topics/engineering/high-efficiency-particulate-air-filter https://www.sciencedirect.com/topics/engineering/high-effici... and an adequately powered one can recirculate room air in 10-15 minuters