I have a close neighbor who is entirely terrible about cleaning his apartment. After his boyfriend broke up with him four weeks ago, he has been a wreck. He doesn’t shower always, he has clothes piling up in the corners on the floor, and I don’t believe he has mopped or vacuumed once since his boyfriend left. The location is starting to smell and I told our neighbor that he needs to clean up or I’m not coming to his apartment anymore. He impressed me and spent a few days slowly chipping away at the whole mess and when he was finally done the place looked fantastic. However, the smell from before he cleaned was still lingering a little and that’s when I thought to ask him if he had changed the A/C filter. He looked at me shocked for a moment and then ran over to his closet. I asked him if everything was okay and that’s when he told me that he realized that he hadn’t even checked the filter once since moving in. He pulled it out of the air handler and all of us looked at it in collective horror. I have never seen a dirtier AC filter in my entire life and I hope I never do. The layer of dirt and grime collected inside was so thick that you could no longer make out the grooves in the filter itself, it was just one ugly grayish brown mass. My neighbor bought a new filter and cleaned out the housing a little with some water and vinegar and now his home smells lovely. He said that his electric bill dropped too since his A/C isn’t now working as hard to keep up anymore.