http://articles.mercola.com/sites/articles/archive/2000/03/12/air-duct-cleaning-unnecessary.aspxAir duct cleaning -- promoted as a service to help prevent allergies caused by dust mites and pets -- appears to be unnecessary, because the ducts that deliver conditioned air throughout a house are almost free of the substances that cause allergic reactionsenCommunityServer 2008.5 SP1 (Build: 31106.3070)