Three standard European soils were artificially contaminated with hexachlorobenzene, 4-chlorobiphenyl, and naphthalene. Small piles (ca. 30 mg) of contaminated soil, or neat soil in control runs, were then heated in the crucible of a thermogravimetric analyzer from room temperature to ca. 450 degrees C at 5 degrees C/min. To investigate effects of ambient gas pressure on contaminants removal, soil specimens were subjected to closely similar heating schedules under either 0.1 or 0.01 MPa pressure of air. The lower pressure augmented decontamination, reducing by as much as 20-45 degrees C the temperature necessary for a given extent of pollutant removal, and increasing the maximum rate of decontamination. The precise magnitude and duration of such pressure-induced improvements in decontamination varied with pollutant and soil type. Predictions of a contaminant evaporation-diffusive transport model were in reasonable agreement with experimentally observed pressure trends. Higher diffusion coefficients for pollutant vapor under reduced pressure are believed to be responsible for the observed pressure effects.