A device for thermal treatment of gases and pollutants employs alternate cavity (1) and susceptor (9) geometries for providing more homogeneous interactions of applied electromagnetic energy (6) in the volume of the susceptor (9) regardless of the flow rate and diameter of the exhaust duct (3) width. The heat transfer methods improve the overall heat efficiency of the device. The susceptor (9) structure has reflectivity as principle mode of interaction with applied electromagnetic energy (6) which allows for energy to penetrate the susceptor (9) which is formed of composite susceptive materials. The use of field concentrators (5) to concentrate the energy density of the applied electromagnetic energy (6) provides a simple methods of controlling trolling the temperature versus energy in the susceptor (9).