A two-dimensional thermally and chemically non-equilibrium model was developed for Ar-N-2-H-2 inductively coupled plasmas (ICP) at reduced pressure. The Ar-N-2-H-2 or Ar-NH3 plasmas at reduced pressure has been widely used for nitriding processing of materials. Totally 164 reactions including 82 forward reactions and their backward reactions were taken into account. Spatial particle composition distribution in the plasma torch as well as in the reaction chamber was derived by solving simultaneously the mass conservation equation of each particle, considering diffusion, convection and production terms. (C) 2009 Elsevier B.V. All rights reserved.