The report reviews briefly the background and development of particulate density measurement systems in the United States and Great Britain and discusses the difference in reporting units which has made it impossible, from routine reporting, to make comparisons of particulate density concentrations in the atmosphere between locations in the U. S., using either gravimetric measurement or light reflection techniques, and locations in Great Britain using the International Smoke Curve for estimating concentration. Procedures for the establishment of a relationship between United States reporting units (COh/1000 ft.) and British equivalent units (microgram/cu meter) have been developed and are described in detail. An exploratory study was made for the purpose of investigating possible relationships between particle count differentiated by size range and particulate density in terms of light transmittance and/or light reflectance. (Author)

"William T. Ingram, Project Director." Funding provided by the Bureau of Disease Prevention and Environmental Control, National Center for Air Pollution Control, Public Health Service. "March 1969." Includes bibliographical references (leaf 70). "PB-206-820"--Handwritten on cover. "APTD-0928"--Handwritten on cover. Microfiche.