Smoke emissions from wild and prescribed fires can be a significant contributor to regional haze and to urban and regional air pollution. Fires directly emit particulate matter; they also emit gases that react in the atmosphere to form secondary organic aerosol (SOA). There is growing evidence that strongly suggests that SOA formed from fire emissions can increase total fire contributions to fine particle mass by a factor of two or more. However, we currently lack an accurate inventory of smoke SOA precursor emissions and the mechanistic understanding to predict the amount of SOA fires contribute to ambient fine particle concentrations at various distances downwind. We also lack ways to directly determine fire SOA contributions to ambient PM2.5 mass. The proposed research addresses these critical uncertainties in order to provide new tools to manage smoke impacts from fire and to quantify those impacts on air quality and regional haze. The objectives of the project are: to quantify SOA production as a function of smoke age in emissions produced by combustion of a variety of important wildland and agricultural fuel types; to quantify emissions of SOA precursors (traditional and non-traditional) in biomass combustion smokes for incorporation into air quality models; to identify compounds quantitatively associated with smoke SOA production to complement use of existing primary smoke markers in determining total fire contributions to ambient PM2.5 carbon; to parameterize the evolution of smoke organic aerosol concentrations for implementation in chemical transport models; to develop simple analytical techniques for SOA markers suitable for use in routine air monitoring networks; and to disseminate project findings to those involved in fire management, air quality analysis, and modeling of smoke impacts. These objectives will be achieved by conducting controlled biomass combustion / smoke aging experiments and by analyzing laboratory samples of fresh and aged smoke and smoke-impacted ambient aerosol samples. The smoke aging experiments, to be performed at the Missoula Fire Science Laboratory and at the CMU campus in Pittsburgh, will feature combustion of both wildland and agricultural fuels. Combustion products (gases and particles) from these fires will be photochemically aged in a smog chamber and the evolution of gas and particle phase pollutants will be tracked using a suite of state-of-the-art instrumentation. The experimental data will be analyzed to quantify SOA precursor emissions and SOA production, assess the contributions by reaction of different SOA precursors, and parameterize aerosol gas-particle partitioning and aging in order to simulate the evolution of smoke plumes using chemical transport models. Chemical markers associated with the production of SOA in aging smoke plumes will be identified using state-of-the-art analytical tools. The goal is to identify markers whose concentrations are related, in a straightforward way, to the amount of additional organic carbon produced during smoke plume aging. To identify these markers we will analyze fresh and aged smoke samples collected as part of the controlled smoke aging experiments. We shall also analyze source samples and smoke-impacted ambient samples archived at CSU. Once suitable SOA markers are identified and their relationships to SOA quantified, we will develop simple techniques suitable for measuring these compounds in samples from routine aerosol monitoring networks. Findings and products from the study, including an inventory of SOA precursor emissions as well as methods for predicting smoke SOA production in air quality models and for determining smoke SOA contributions to ambient PM2.5, will be shared with the smoke management and air quality communities through a variety of venues including peer-reviewed publications, conferences and workshops, and a project website.