Two different types of performance testing systems are used to measure duct leakage: a duct blaster test or a blower door test.

A duct blaster combines a small fan and a pressure gauge to pressurize a home’s duct system and accurately measure air leakage of the ductwork. This test is similar to a pressure test of a plumbing system. Duct leakage can increase heating and cooling costs over 30% and contribute to comfort, health and safety problems. Here is how the test works:

• A duct blaster is used to directly pressure test the duct system for air leaks, much the same way a plumber pressure tests water pipes for leaks.
• The duct blaster fan is first connected to the duct system at the air handler cabinet, or a return grille. After temporarily sealing all remaining registers and grills, the duct blaster fan is turned on to force air through all holes and cracks in the ductwork.
• The fan speed is increased until a standard test pressure is achieved in the duct system. A precise leakage measurement is then made using an airflow and pressure gauge connected to the duct blaster system.