The paper discusses experiments on a 17-kW downflow combustor to determine how sorbent injection into the postflame influenced the particle size distribution of a lead (Pb) aerosol formed from a surrogate Pb-containing waste. In the absence of chlorine (Cl), the Pb aerosol size distribution evolved within the combustor to lie predominantly between 0.02 and 0.2 micrometer by the time it was sampled at the combustor exit. When a commercial kaolinite sorbent was added, the Pb sampled in that particle size range was reduced by 99%, and it is clear that the heavy metal was reactively scavenged in the combustor by the larger sorbent particles. Cl kept the Pb in vapor form until it was sampled, at which point it formed a fume in the probe. At large Cl/Pb ratios (> 10), adding sorbent was not effective in scavenging the Pb vapor, although capture was again apparent as Cl/Pb ratios were reduced to 2. Data from experimental runs with a large excess of Cl present, but not those where the Cl/Pb ratio was equal to 2, are in sharp contrast to literature data from bench scale reactor studies. (Copyright (c) 1992 M. A. Scotto.)