This thesis is based on an extensive air quality study in homes with attached garages conducted by Health Canada in Ottawa, Ontario. The thesis used source apportionment modelling to resolve sources that contribute to the home, garage and ambient volatile organic compound (VOC) concentrations, providing insight to common sources and infiltration between these microenvironments. Six sources were identified for each sampling location including those related to global persistent compounds, fuel and other combustion processes, fuel evaporation and solvent use. The presence of these factors in more than one microenvironment combined with the statistical analysis conducted using correlations and ratios confirmed the likelihood of infiltration between the microenvironments. This research supplements the Health Canada study and provides an alternative avenue for reducing the VOC concentration in homes by providing the opportunity to eliminate point sources within the home and garage.