In recent years, Environmental Protection Agency (EPA) has learned that caulking materials containing potentially harmful polychlorinated biphenyls (PCBs) were used in many buildings, including schools, in the 1950s through the 1970s. On September 25, 2009, EPA announced new guidance for school administrators and building managers with important information about managing PCBs in caulk and tools to help minimize possible exposure. EPA also announced additional research into this issue to address several unresolved scientific questions that must be better understood to assess the magnitude of the problem and identify the best long-term solutions. For example, the link between the concentrations of PCBs in caulking materials and PCBs in the air or dust is not well understood. The Agency is also conducting research to determine the sources and levels of PCBs in schools and to evaluate different strategies to reduce exposures. The results of this research will be used to provide further guidance to schools and building owners as they develop and implement long-term solutions (U.S. EPA, 2009). The EPA research on PCBs in schools is designed to identify and evaluate potential sources of PCBs in order to better understand exposures to children, teachers, and other school workers, and to improve risk management decisions. Specific research areas include characterization of potential sources of PCB exposures in schools (caulk, coatings, light ballasts, etc.), investigation of the relationship of these sources to PCB concentrations in air, dust, and soil, and evaluation of methods to reduce exposures to PCBs in caulk and other sources (U.S. EPA, 2010). As part of the EPA research effort, this report summarizes the test results for PCB emissions from primary indoor sources, with emphasis on PCB-containing caulking materials and light ballasts, and the factors that may affect the emissions. Subsequent reports will discuss the research results on PCB transport in buildings and evaluation of selected mitigation methods. The main objectives of this study were to seek a general understanding of the behaviors of the primary PCB sources in buildings, especially caulking materials and light ballasts, to support risk management decision making by providing new data and models for ranking the primary sources of PCBs, and to support the development and refinement of exposure assessment models for PCBs, such as the Stochastic Human Exposure and Dose Simulation (SHEDS) model, by reducing uncertainty in the models.