Turn on the air conditioning system and return to areas where ducts can be accessed. Check the connections between each section of the duct and place your hand on the metal. If you feel air in your hand, the connection is loose and there is an air leak. To check for holes and leaks, look for visible holes, bent or twisted ducts, and loose connections in the ductwork.
This can be done with the naked eye or with a flashlight to make it easier to detect leaks. Duct testing involves sealing an entire ventilation system and then pressurizing it to determine how airtight it is. Technicians determine how much air pressure escapes from ducts and then track locations so they can repair or seal them. HVAC duct tests are used to detect leaks in ducts.
There are two types of duct tests: duct pressure or leak (DP) tests and outdoor leak pressurization (LTO) tests.