They have never been cleaned before. Most homes have never had their air ducts cleaned. Indoor air may be up to 70 times more polluted than outside air.
You or your family members have allergies. Dust and other contaminates are actually pulled into your furnace system through the return air side of the system. Heating air ducts systems provide ideal breeding grounds for bacteria, mold, fungi, and other allergens. As an example: dust mites breed in temperatures between 72 and 86 degrees. Children under four (with immature immune systems) are particularly under attack and the result may be allergies or asthma. Seattle Healthy Projects reports. “New research indicates if children do not come into contact with Asthma triggers between birth and 4 years old they may never develop asthma.
You have had a wet, damp, or flooded basement in the past – causing mold and mildew growth.
You want to clean out all those living and dead spiders, insects and rodents that have been living (dying) in your ducts for years.
You have had remodeling done in you home. Remodeling dust can circulate for years.
Pet fur gets caught in the vents and builds up living germs, fungus, and allergy-causing elements, giving mold and mildew something to live on.