As we spend most of our time in buildings, understanding sources and composition of indoor air pollutants is fundamental for interpreting the health risks and for developing improved building control measures to mitigate human exposure. This theme specifically focuses on better understanding of air pollution dynamics in proximity to people, including identifying role of humans and their activities in influencing indoor air composition, underlying transmission mechanisms to lungs and resulting inhalation exposures. The efforts also include application of novel methods to better understand mechanistically the relationships between air pollution sources and consequent exposures. The topics also includes longitudinal assessment of human personal exposures in dynamic environments and quantifying the role of humans in influencing indoor air composition, which is important for understanding how particles and chemicals are transmitted to people and might be better controlled.