A simple model for carbon monoxide in gas turbines is developed. For typical engine idling and full power conditions the model examines the effect of the parameters equivalence ratio, residence time and degree of mixing on both the equilibrium carbon monoxide concentration and the approach to this level within the various regions of the combustor. The model is largely intended to be interpretive rather than predictive, but the curves presented enable one to qualitatively follow reported trends in carbon monoxide emission levels with the above parameters. Finally suggestions are made for minimizing carbon monoxide emissions at the idling condition.