This is not a TIL for me, but for my wife.
I started working nights again and sleeping during the day can be challenging, and for me one of the most challenging things is that it is hotter and I really like to be cool when I sleep (sleep experts say you sleep better when it's cool, and they say "cool" is probably colder than you think, between 64f and 67f is the optimal temp for good sleep). So I've been turning the thermostat down before I go to bed, then my wife gets cold and turns it up. My bedroom gets hot really fast and stays a lot hotter than the rest of the house.
So long story short, I'm looking for a portable room air conditioner. I don't want a window unit because I have my window extra super triple blacked out. But even the portable units need to exhaust the hot air. I figured I could exhaust to the bathroom fan in the master bathroom. So I was telling my wife that and she was a little bit confused. It then became clear that she didn't know those fans exhaust to the outside. So I'm explaining that and telling her that they are there to help prevent mold since it gets humid when you shower.
She finally asks "So they pull air in?" I was a little confused and repeated that they are there to remove humidity. She says she always thought they blew air into the bathroom, that they were just fans.