Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

A Method of Test for Tracer Gas Test of an Outdoor Furnace Designed for Installation Without a Flue Pipe



S T. Liu, George E. Kelly


An induced draft, gas-fired furnance orignally designed for outdoor installation without a flue pipe was tested by the tracer gas method to determine its off-cycle power burner draft factor. This report describes the feasibility of attaching a short flue pipe to the outside furnance during the optional tracer gas test in facilitating test measurement without significantly increasing the measured power burner draft factor due to the stack action of the added flue pipe during the burner off period. The results showed that it is possible to conduct the tracer gas test with a short attached flue pipe to facilitate the test without changing the calculated results for the value of Annual Fuel Utilization Efficiency (AFUE). Therefore, it is recommended that a short flue pipe, between 0.2m to 0.3m (8 in. to 12 in.), be allowed in the DOE furnace test procedure for the optional tracer gas test for outdoow furnances desgned for installation without a flue pipe.
NIST Interagency/Internal Report (NISTIR) - 6257
Report Number


Annual Fuel Utilization, Building Technology, DOE test procedures, Efficiency, Flue Pipe, Induced Draft Furnace, Outdoor Installation, Power Burner Draft Factor, Tracer Gas Test


Liu, S. and Kelly, G. (1998), A Method of Test for Tracer Gas Test of an Outdoor Furnace Designed for Installation Without a Flue Pipe, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 17, 2024)
Created November 1, 1998, Updated February 19, 2017