According to the National Air Duct Cleaners Association (NADCA), an average six-room home collects 40 pounds of dirt, dust and allergens in its air ducts each year! That’s a disgusting problem, considering that 40,000 dust mites can thrive in only one ounce of dust. Dust “bunnies” contain a host of unhealthy bacteria, fungi and mold. What is even worse, is that contaminated air circulates throughout your house every time the heating or cooling system kicks on.