The first thing I do every time I step into a hotel room is check the filter. If it’s dirty, then I bring it to the front desk to show them. I always get a free upgrade… to another room with an equally dirty filter. Which at that point I remove it and toss it in the stairwell to let it be maintenance’s problem. I can’t be bothered to put in more effort than that if the staff can’t be bothered to replace their filters.