The answer to 'air duct stained' is that stained air ducts are a common issue that can be caused by a variety of factors, including dust buildup, mold growth, and even pests. Stained ducts can not only look unsightly, but they can also negatively impact your indoor air quality and the efficiency of your HVAC system.
Some common symptoms of stained air ducts include visible discoloration or staining, musty odors, and reduced airflow from your vents. In many cases, these issues can be addressed through regular maintenance and cleaning, but in more severe cases, you may need to call in a professional duct cleaning service.