The central air duct system in your home acts exactly like the lungs of our respiratory system; drawing in and circulating the air throughout the house. As it moves the air around, however, the air duct system is continually collecting and distributing household dusts, which may contain dead skin cells and animal dander, dust mites, bacteria, mould and mildew, etc.
To maintain good air quality in your home it is recommended that you have your ducts cleaned by a professional every 3-5 years. If anyone in your home suffers from the symptoms of asthma, allergies and other respiratory conditions, having your ducts cleaned every 1-2 years may help to alleviate symptoms significantly.