Report Number




Ducts; Buildings


A methodology is presented for using tracer gas testing to detect and quantify duct leakage in homes. Since air is invisible, leakage of air from duct systems often remains undetected. Smoke sticks used in conjunction with blower doors are excellent diagnostic tools for detecting and locating leaks in the air distribution system. The tracer gas tests described are a good complement to these tools in the detection, location, and measurement of duct leakage.

Testing for house infiltration once with the air handler on and again with the air handler off indicates whether duct leaks exist. In many cases, it is possible to determine the leak flow rate. A second part of the test, determining the return leak fraction by comparing the tracer gas concentration at the return and at a supply, can provide more accurate determination of the leak flow rate and whether it is a supply or return leak.

The tracer gas test methodology enables fairly accurate assessment of the energy impacts of the leaks and whether repair will be cost-effective. Finally, the tracer gas test can be repeated after repairs have been completed to ensure that the duct leaks have been sealed.

Date Published



Reference Publication: Cummings, J.B., "Tracer Gas as a Practical Field Diagnostic Tool for Assessing Duct System Leaks", Proceedings of 6th Annual Symposium on Improving Building Systems in Hot and Humid Climates, Dallas TX, October 1989. (FSEC­PF­195­90)

Local Subjects

Buildings - Ducts


FSEC Energy Research Center® Collection



Rights Statement

Copyright Undetermined