Thermophoretic effect on particle deposition velocity onto an inverted flat surface was numerically investigated, by employing the Statistical Lagrangian Particle Tracking (SLPT) model. The SLPT model was verified to be correct, when the numerically obtained particle deposition velocities were compared with the theoretically predicted particle deposition velocities, with and without considering thermophoresis. Temperature difference between flat surface and ambient air, particle density, and airflow velocity were found to affect the particle deposition velocity onto the inverted flat surface under the influence of thermophoresis. Thermal conductivity ratio between air and particle, however, was found to be insignificant in affecting the particle deposition velocity onto the inverted flat surface. Particulate contamination of the inverted critical surface was estimated to be greatly reduced by heating the surface. On the other hand, the face-down critical surface was anticipated to be contaminated by particles when the surface temperature was lower than the ambient temperature, even with the scheme of inverted orientation. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3621720] All rights reserved.