Back to Training HVAC 101 0% Complete 0/0 Steps Dampers Explained Insulation Check Finding Signs Of Rats In The Attic Space Drawing A System Duct Inspection Heating Sequence Of Operation - Standard Furnace Ladders, Drops & Attic Access 5 Inch Media Filter Replacement Remove Locking Refrigerant Caps HVAC 101 Remove Locking Refrigerant Caps Video 9 of 9 In Progress ← Previous Remove Locking Refrigerant Caps These caps help prevent leaks and require a special HVAC key to access.