The answer to 'why is my air duct pet stains' is that pet dander, hair, and waste can accumulate in air ducts over time. This can lead to visible stains and odors in the ductwork. Common causes include pets shedding, using the ducts as a litter box, or pets scratching at the ductwork.
The symptoms of pet stains in air ducts include discoloration of the ductwork, musty odors, and poor air quality. This can impact your home's cleanliness and the health of your family, especially those with allergies or asthma.