A coordinated study of process, source emissions, and plume sampling was conducted at a coal-fired cement production plant. Both source and plume sampling consisted of particle and gas measurement and characterization. Particulate sampling of both the source and plume addressed particle size, amount, and composition. Particles were analyzed by scanning electron microscopy, x-ray fluorescence spectroscopy, and chemical means. Gas sampling of both the source and plume involved conventional source sampling methods as well as procedures adapted to this specific measurement program. Plume opacity was measured by visual observation and a LIDAR system. Comparison of the results from the plume and source measurment indicated the formation of the plume was the result of the reaction of ammonia and hydrochloric acid. The formation of ammonium chloride occurred within the same set of reaction parameters as independent laborabory studies had previously indicated.