Includes:10 Vents,Free Unlimited Mains(WAS $50.00 EACH) Free System Inspection!Sears uses a negative air flow process with truck-mounted or HEPA-filtered vacuums. We clean all ducts and returns with air blowers, brushes and/or whips pushing debris to vacuum. All access holes are replaced according to NADCA specifications.Additional vents $20.00 each.