As a landlord I have seen just about anything plus everything when cleaning out locales once a occupant has vacated.
I have had to replace flooring detrimentd by pets, redone plumbing that was plugged or detrimentd by irresponsible people, plus even had to pay for industrial cleaning in some cases, and this last issue almost had me giving up on they whole process entirely.
Sure, I was able to keep the security deposit, but, that didn’t come close to covering the cost involved in repairing the Heating, Ventilation, plus A/C system. Not only did I have to have the air duct cleaned due to the stash of drugs we found tucked in the vents, I had to have the machine repaired because they had kept it running non stop with a humidifier set up to help grow the plants in the basement. They had plugged off many of the air vents with cardboard so that the heat could be directed to the growing section more easily. This had causes a build up of debris at the opening of the vents that can only be described as gross. I had to make sure that the Heating, Ventilation, plus A/C system was clean plus safe before I could rent the machine to anyone else. I have changed my rental agreement to include annnual inspections because I want to ensure that occupants are not damaging my proberty like that again in the future. I know it solves the mystery as to why the previous people never complained about anything or asked me to fix anything. They didn’t want me to see what was honestly going on in the apartment. I won’t make that mistake again.