This paper describes the ongoing development of a new tracer gas test (TGT) for total air change rates measurement. This new TGT, intended for use in large-scale IAQ assessments and based on constant tracer injection, employs an alternative tracer gas that is more adequate than the currently employed SF6 and perfluorocarbons and that can be co-captured and co-analyzed along with commonly assessed VOCs using a commercial passive IAQ sampler. Via literature study and lab testing, decane-D22 was found to be a suitable tracer substance. Several laboratory tests have been performed under controlled environmental conditions to develop and optimize a passive source of decane-D22. The source design ultimately selected provides stable and repeatable emission rates under standard temperature and is unaffected by RH. A series of chamber tests were performed under different temperatures, and a consistent exponential curve was derived for determining the source emission rate from the room temperature. Future work includes field test applications for validation of the new TGT.