The plume rise equations of Briggs (1975) for variable vertical profiles of temperature and wind speed are described and applied for hypothetical small and very large chimneys at five NWS rawinsonde stations across the United States. From other available data additional information on plume behavior is deduced. For example, based on the 0515 CST soundings at Nashville, 61% of the effective plume heights for 50-m chimneys were in a temperature inversion, but only 21% for 400-m chimneys. Ordinarily such plumes would be in a fanning configuration. Most of the plumes from large chimneys (60%) were above an inversion, probably in a lofting mode. Overall, 98% of the small plumes were reached by the afternoon mixing height, but only 85% of the large plumes were reached. Such information supports the obvious presumption that the effluent from large chimneys remains airborne longer than that from small chimneys, is transported over greater distances, and has more opportunity to undergo chemical transformations.