Atmospheric particulates consist of solid particles and liquid droplets ranging in size from millimicrons to tens of microns and varying shape from spherical fog droplets to porous and irregular soot particles. Particulates are considered pollutants inasmuch as they can reduce visibility, cause property damage, and produce toxic effects both in man and plant life. Instrumentation is necessary, to evaluate the contribution of man-made particulates to the air pollution problem, the nature of various particles and their correlation to specific effects, and the effectiveness os specific control measures. The report discusses the photoelectric measurement of light scattered by particulate. The method offers a sensitive method of analysis without some of the drawbacks of sample collection.