At the outset of the SARS-CoV-2/COVID-19 outbreak in China, researchers identified an airconditioned five-story windowless restaurant common to ten cases of infection.
The study concluded the key factor for infection was the direction of the airflow. The researches also stated, “Virus transmission in this outbreak cannot be explained by droplet transmission alone.”
Ventilation, the lack thereof, was a factor, but the direction of airflow was the key factor.
Read the full report here: CDC, 7 July 2020 | COVID-19 Outbreak Associated with Air Conditioning in Restaurant, Guangzhou, China, 2020
How is the direction of airflow important? If you, a non-smoker, have been on the receiving end of secondary smoke, you can imagine being on the receiving end, the downstream of an airborne pathogen.
In surgical rooms where open-heart surgery and like invasive procedures are carried out, HVAC designers arrange HVAC air distribution devices to create a one-pace route for conditioned air to pass over the patient.
This simple design tactic applied to other habitations can be a significant preventive against airborne pathogens.
John N. White 
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