TU > how much viral load would there be floating around without ventilation and what % is rendered non-viable or is expelled altogether
Rather than relying on the studies, I did tests myself using air quality monitor:
A fully closed small office with 6 computer seats and reasonable ventilation: CO2 level stays normal with 1 person, starts going up after 10 minutes with 2 people. With one door open to an internal corridor, stays normal with 3 people. PPMs stayed low in all cases (except when there was a BBQ outside), that is this particular HVAC was filtering something out, but HVAC outside air intake is low.
A shul with 10 people with place for 40 – CO2 goes up with HVAC and everything closed. Is normal with a door and 3 windows half-open.
This adds – just opening the door to the corridor helps.