Microwave discharges at 2.45 GHz frequency and accelerated electron beams operated at atmospheric pressure in synthetic gas mixtures containing N-2, O-2, CO2, SO2, and NOx are investigated experimentally for various gas mixture constituents and operating conditions, with respect to their ability to purify exhaust gases. An original experimental unit easily adaptable for both separate and simultaneous irradiation with microwaves and electron beams was set up. The simultaneous treatment with accelerated electron beams and microwaves was found to increase the removal efficiency of NOx and SO2 and also helped to reduce the total required dose rate with similar to30%. Concomitant removal of NOx (similar to80%) and SO2 (>95%) by precipitation with ammonia was achieved. (C) 2002 Elsevier Science B.V. All rights reserved.