The Disturbing Smell of a Hotel Room

My mom got assigned to clean his room on the daily but as time went by, she noticed that he always had the do not disturb sign up on his room. This didn't bother the cleaning staff too much because the way my mom tells it, the guy was always super nice and friendly whenever he passed reception or bumped into any of the cleaning staff. So if it saved them some work, they weren't exactly going to complain about it. Anyways, there came a point where the guy wasn't seen for a few days so everyone figured that he just checked out and they'd be able to clean the room again. So given that my mom had been assigned to the room like a month