The Home Inspector San Diego
A duct test is controlled fan that is hooked up to a speed controller. A duct is attached from the speed controlled fan to the return air of the HVAC system. The supply ducts are sealed off and the duct tester then is turned on. One reference hose from the dual channeled manometer is attached to the fan and another is placed in the supply air system. .
This data is then analyzed by a dual channel manometer to give results in real time.
All ducts have leakage. The Air handler or HVAC box also leaks. The purpose is to limit the leakage and have the conditioned air from the HVAC unit go where intended to your home