Back to Training HVAC 101 0% Complete 0/0 Steps Remove Locking Refrigerant Caps 5 Inch Media Filter Replacement Ladders, Drops & Attic Access Heating Sequence Of Operation - Standard Furnace Duct Inspection Drawing A System Finding Signs Of Rats In The Attic Space Insulation Check Dampers Explained HVAC 101 Dampers Explained Video 9 of 9 In Progress ← Previous Dampers Explained Ducts connected at the plenum and t-wyes may have an internal damper that can be adjusted to regulate the amount of air and pressure each duct can achieve.