Funds from this grant support work by atmospheric chemist Paul Ziemann to expand our understanding of chemical sources, sinks, and transformations of indoor environments, and to develop physical-chemical mechanisms to describe these processes. Ziemann will conduct a series of pilot studies to examine a range of indoor environments. His studies will aim to (1) identify similarities and differences in the organic chemical composition of indoor gases, particles, and surfaces; (2) determine organic chemical contributions from various sources; (3) determine the effects of organic gases, oxidants, acids, humidity, light, and temperature on gas, particle, and surface composition; (4) determine potential effects of organic compounds emitted by humans, either directly or as a result of reactions; and (5) develop physical-chemical mechanisms to explain observed compositions and processes. The range of indoor environments to be tested includes an art museum, classrooms, offices, a student athletic center, student dining facilities, and local residences. This project will provide new insights into the physical and chemical processes that determine the composition of indoor air and allow for development of a deeper understanding of how different indoor environments function. The results also promise to be valuable for developing models for predicting the chemical composition of indoor air and strategies for improving indoor air quality. The results will be shared through peer-reviewed publications and presentations at conferences and meetings. At least two students and one postdoctoral fellow will be trained.