I was putting all my chai tea into a container – taking apart the tea bags and dumping the tea itself in.
It was potent (mom complained) and the people upstairs decided to spray bad perfume into the heat return (so it’s recirculated into the house).
Mom thought the smell was so bad she turned off the furnace.
I turned it back on about half an hour later and the smell was still raunchy… so I plugged their air return.
5 minutes later and the smell is all but gone.