A modelling study of combustion inhibition in an idealized well-stirred reactor utilizing H2/O2/Ar mixtures as the reactants is presented and discussed. The effect of two chemical inhibitors, HCl and HBr, on the combustion process has been investigated at pressures of 0.01 and l.0 atmosphere over a range of equivalence ratios of 0.5 to 1.5 and inhibitor concentrations of 0 to 10 percent. Inhibitor effectiveness was determined by the competition between the radical scavenging ability of an inhibitor and the exothermicity of the scavenging reactions. For all cases considered HBr was more effective in scavenging active radicals than HCl. At 0.01 atmospheres, HCl was a more effective inhibitor in lean and stoichiometric mixtures while HBr was more effective for rich mixtures at 0.01 atmosphere and for all atmospheric pressure mixtures.