They installed two of the same side barn door in our hotel bathroom. Gay.

Me, on a clear 60F day, listening to the makerspace furnaces

This is an air admittance valve. Also known by some as a vacuum breaker. You generally see them on Plumbing drain pipes where a lot of water enters the drain at one time like washing machines or dishwashers. I just grabbed food from a Hardee's drive-thru and noticed through the window they had a cup turned upside down covering one up. When I said something they of course had no idea what I was talking about. I really hope there's not some problem with their drains. 

JFC don't do this you fucking boomers

No I didn't buy it

Heh