The answer to tough stains on air ducts is that there are several common causes, including dust buildup, pet dander, and grease from cooking. Symptoms may include visible stains, reduced airflow, and a musty odor. Solutions can range from DIY cleaning to professional duct cleaning, depending on the severity of the issue.
For light stains and dust buildup, homeowners can try DIY cleaning methods like vacuuming the ducts with a hose attachment or using a damp cloth to wipe down the visible areas. However, for more stubborn stains or significant buildup, it's best to call in a professional air duct cleaning service. They have the specialized equipment and expertise to thoroughly clean the entire duct system and remove all traces of tough stains.