Interesting paper with good methodology, but It mentions residents coming and going via stairs and the front door. So I guess they were not locked down in their apartments with food being delivered. They probably used the same laundry room as well. I think there are so many other opportunities for transmission that this investigation is rather silly. You can find anything if you look hard enough.

The PCR CT values are going to reflect the fact that infected people shed virus, and that mostly ends up on the floor or other horizontal surfaces as droplets fall. I'm sure infected residents also shed aerosols, since particles of all sizes are exhaled, coughed, sneezed, etc. "Exposure" has been defined as being within six feet of an infected person for 15 minutes in an enclosed space. But these residents were effectively exposed to others' aerosols for several days, probably over 12 hours per day! This is similar to studies of secondary transmission within households: It's a very low bar to get infected from people you are living with in the same enclosed space.

Yes, aerosol transmission is possible, and very likely if you live in the same household as an infected person. From strangers you encounter, masked, in an elevator? Very unlikely. It requires very unusual circumstances, and that's why this paper is pretty unique. But even in this apartment building, they say 14 of the 19 infections were caused by social interaction with one infected individual.

But it is a very good idea to put some water down every sewer trap now and again, since they leak sewer gases into your house and stink.

Educating anyone benefits everyone.