The answer to 'why is my air duct dusty' is that air ducts can accumulate dust, dirt, and other debris over time, leading to a buildup in the system. This can be caused by a few common factors, such as poor air filtration, inadequate duct cleaning, and general wear and tear on the system.
Dusty air ducts can lead to reduced air flow, decreased energy efficiency, and even the circulation of allergens and pollutants throughout your home. Regularly cleaning and maintaining your air ducts is important to ensure good indoor air quality and optimal HVAC system performance.