>A door stops airflow? No.

I mean, it literally does. Put something that smokes in a bathroom, open the window, close the door, and caulk the gaps. See how much smoke phases through the door.

I forgot HN isn’t exactly the demographic that tries this and finds out exactly how well it works. I guess for this demographic, I’d suggest telling your tenants it’s okay to smoke in the bathroom as long as the door is closed and the fan is on.