The purpose was to simulate on a laboratory scale the time-temperature profile of a central-station power plant and the early plume. A multipurpose furnace fired either with pulverized coal or with residual oil; a simulated boiler/economizer section; an electrostatic precipitator for use with coal firing; a stack section, in which temperature distribution was controlled independently by electrical heating; and a dilution and expansion chamber to simulate the early stages of plume development were used. The objectives were: Identification of sections of the system wherein major depletion in SO2 could be observed; Determination of the effect of fuel type on SO2 depletion; Determination of the significance of the contribution of fly ash to the overall SO2 depletion; investigation of the rate of oxidation of SO2 in the early stages of plume development; and Assessment of the effects of relative humidity, temperature, and process variables on the rate of SO2 loss in the early plume. First-order rate constants for the decay of SO2 in the plume agreed with those found by other investigators. (Author)