Porous media VOC oxidizing reactor, consisting of coaxial tubes system with counter-flow heat exchange and embedded electric heater, is under investigation. Influence of heater configuration and power, gas flow rate and thermal isolation on maximum temperature in reactor and unburned VOC concentration is determined numerically. It is shown that axial configuration of the heater is more effective than the circular one in the case of high flow rates U-G similar to 1m/s or more. Minimum unburned VOC is reached if axial heater end is set at the level of the central tube edge. Practical porous media VOC oxidizer was simulated for the aim of the mathematical model verification. Comparison of simulated and measured non-steady temperature fields in the reactor during startup demonstrate reasonably good agreement (10-20%). (c) 2006 Elsevier Ltd. All rights reserved.