The study objectives were to improve the understanding ofthe long-term variationofVOCemission chromatograms of building materials and to develop a method toaccountfor this variation in the identification of individual sources ofVOCemissions. This is of importance forthe application ofthe source identification method since materials age over time in real indoor environments. The method is based on the mixed air sample measurements containing pollutants from multiple aged materials and theemission signatures ofindividual new materials determined by PTR-MS. Three emission decay source models were employed and evaluated for their ability to track the change of individual material emission signatures by PTR-MS over a nine-month period. Nine building material specimens were studied in a ventilated 50-L small-size chamber for their emissions individually for nine months, and also in combination later. Chamber exhaust air was sampled by PTR-MS to construct a temporal profile ofemission signature unique to individual product type. The similar process was taken to measure mixture emissions from multiple materials, which is for applying and validating the developed method for source identification enhancement, considering thevariation in long-term emission rates of individual VOCs. Results showed that the proposed approach could predict theemission signatures of individual building materials at a later time (9-month) with less than 6% difference variance, and hence indicated the potential ofthe source identification method for aged materials in real indoor environments.