Ventilation is critical in interpreting indoor air quality (IAQ), yet most IAQ assessments do not report ventilation adequately. Most ventilation assessments use tracer gas tests (TGT) to measure total air change rate (ACH), but currently applied TGTs present three shortcomings: limited comparability between ACH and IAQ data, inadequate substances employed as tracer gases and tendency to bias arising from perfect-mixing assumption. This paper proposes a new TGT approach, employing an alternative tracer gas that is captured/analysed using commercial passive IAQ-samplers and including a careful planning-phase to account for imperfect-mixing. Two substances were selected as potential alternative tracers: 2-butoxyethyl-acetate (EGBEA) and deuterated decane (D-decane). Tracer-source tests were performed in lab, enabling enhancements to the source design. Results indicated RH influence over the emissions rates, and EGBEA's use as tracer was discarded due to hygroscopy. Further work includes evaluating D-decane's behaviour under varying conditions and computer-simulating TGTs to study the imperfect-mixing effects.