A model of particle impingement on, and reflection from, surfaces is proposed. For smooth electrostatic precipitator collector surfaces, the model is combined with a calculation of the turbulent burst phenomenon, and particle re-entrainment obtained for typical precipitator operating conditions. For collector surfaces with plate baffles, the model was combined with a calculation of the recirculating flows fore and aft of ribs obtained by numerically solving the elliptic forms of the governing conservation equations using a k-epsilon turbulence model. Plates baffles reduce particle re-entrainment but increase particle diffusivity near the collector surfaces. Thus, for larger particles (d(p) greater than or similar to 1 mu m) for which re-entrainment may be significant, the baffles should increase the precipitator collection efficiency. However, for small particles (d(p) less than or similar to 0.5 mu m) for which re-entrainment is insignificant, the baffles should decrease collection efficiency.