The addition of NO (0 to 400ppm) to mixtures of H2 (ca. 1%) and O2 (0.7 to 22%) has been studied over the temperature range 700 to 825 K, in a flow reactor at atmospheric pressure. The overall effect of NO is to promote the oxidation of H2 but high concentrations of O2 actually inhibit the NO‐promoted oxidation of H2. A detailed kinetic mechanism has been constructed and found to describe the experimental observations. The promotion of the oxidation of H2 arises through the catalytic cycle (Formula Presented.) The ability of R.34 to reactivate chains normally terminated by the formation of HO2 is a key feature of this system. The predictions are highly sensitive to the rate of the reaction R.5 and the rate constants for this reaction is the only adjustable parameter required in the model. The value of k5,N2 found to describe all the results (Formula Presented.) has an absolute uncertainty <35%. The uncertainty relative to other important rate constants in the H2O2 system is less than 10%. © 1995 John Wiley & Sons, Inc.