Never heard of transmissions through ventilation systems?Would love to see the evidence that backs that one!
Generally we just don't see that type of transmission. There was a condo in Calgary that was in the news for a while for a large outbreak, but I never saw any reliable source suggest it was being transmitted between multiple units and building outbreaks weren't common. My grandma's ward had a COVID outbreak, she was tested numerous times, had pneumonia but never COVID.