Outbreak investigation of airborne transmission of Omicron (B.1.1.529) - SARS-CoV-2 variant of concern in a restaurant: Implication for enhancement of indoor air dilution
In May of 2021, Hong Kong required air purifers be placed in their restaurants after papers like this showed that you could be infected in just 19 minutes, median exposure time 34 minutes, while eating at a restaurant.