ACH = Air Changes per Hour.
The best protection against an acute airborne threat like COVID-19 is eliminating it from the air as quickly as possible. The equivalent ACH calculation provides you with a single metric that represents your bottom-line protection for a given pathogen.
For sufficient safety from cross-infections by airborne SARS-Cov-2 a minimum ACH of 6 to 12 is recommended by CDC, ASHRAE & NIOSH.
(SpaceUV systems helps achieve upto 24 equivalent ACH!)