The answer to 'why is my air duct buildup' is that air ducts can become clogged with dust, dirt, pet hair, and other debris over time. This buildup can restrict airflow, reduce your HVAC system's efficiency, and even lead to poor indoor air quality.
Some common causes of air duct buildup include lack of regular cleaning, old or damaged ductwork, and the presence of pets or smokers in the home. Symptoms may include reduced airflow, higher energy bills, and increased dust or allergens circulating in your home.