Technical Bulletin No. 0066: Factors Controlling Formation and Persistence of Ground Level Visibility-Reducing Moisture Plumes (AQTB)

Increasing attention has been paid in recent years to the identification of those meteorological conditions which when occurring account for the condensation of moisture in particulate free exhaust gases and result in reduction of visibility at ground level. Essentially all this effort has been focused on large volume sources such as air passing through natural draft cooling towers. Manufacturing operations in various industries discharge moist exhaust gases, free of particulate matter, which might reduce ground level visibility, which are much smaller in volume than air from natural draft cooling towers. The work described in this Technical Bulletin was directed toward (a) defining the factors responsible for formation of visible plumes from sources such as these, (b) deter mining if meteorological conditions which may result in reduction of ground level visibility from their presence exist, and (c) identifying possible remedial measures for those situations warranting corrective action. The investigation was conducted by Edward Miller, Mark Fair, and Peter Murray under the direction of Prof. E. Wendell Hewson, Chairman, Department of Atmospheric Sciences, Oregon State University.