Human activity patterns result in indoor environments playing an important role in exposure outdoor air pollution. In tropical climates, building ventilation conditions and occupant preferences may dramatically affect exposure to particulate matter and ozone, as many buildings rely on natural ventilation for cooling at least some portion of the day. We model exposure to particulate matter (PM) and ozone (O3) in five microenvironments with varying indoor/outdoor PM and O3ratios across three regions of Singapore. Results show that geographic variations in outdoor concentrations of PM and O3contribute to a factor of two difference in daily exposure across age subgroups while differences between more protective and less protective microenvironments result in a factor of three difference in daily exposure.