A stainless-steel gliding arc reactor with the reaction space modified to assume a rectangular cross section and the electrodes shorter than those in quartz reactors, was used to convert 2.5, 5 or 10 vol% N2O-O-2 into NO. At 200 L(S.T.P.)/h, a 2.5% N2O gas was converted into NO in 50%. The total degree of conversion was 82%.