DavidElfstrom, This paper reports transmission occurring after 4 hours of vacancy in a room with 6 ACH ventilation measured at some undisclosed time before the outbreak.
24 air changes (6 ACH x 4 h) is a 99.999999996% reduction. Highly improbable to infect. More likely the actual ventilation rate was much lower at the time. https://www.ajicjournal.org/article/S0196-6553(24)00162-7/abstract