The objectives of this study were to characterize the changes of VOC material emission profiles over time and develop a method to account for such changes in order to enhance a source identification technique that is based on the measurements of mixed air samples and the emission signatures of individual building materials determined by PTR-MS. Source models, including power-law model, double-exponential decay model and mechanistic diffusion model, were employed to track the change of individual material emission signatures by PTR-MS over a nine-month period. Samples of nine typical building materials were tested individually for nine months and later in combination to obtain actual mixture emissions. VOC emissions from each material were measured in a 50-liter small-scale chamber. Chamber air was sampled by PTR-MS over a 28-day period to determine their emission rate decay characteristics as well as to establish the initial profile of emission signatures unique to individual materials tested.