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Carbon monoxide concentrations and mixture fractions were measured in the fuel-lean (over fire) region of turbulent acetylene, propylene, ethylene, propane and methane diffusion flames burning in still air. Three burners (having exit diameters of 5,50 and 234 mm) were used to study conditions ranging from buoyant jet flames to pool-like fires. Carbon monoxide generation factors (mass of CO emitted per unit mass of fuel carbon burned) were uniform throughout the over fire region for a given flame condition. Additionally, CO generation factors of sooting fuels approached asymptotic values for flame residence times roughly an order of magnitude longer than the normal smoke point residence time, similar to earlier measurements of soot generation factors for similar conditions. Finally, processes of carbon monoxide and soot emission appear to be closely related due to the good correlation between their emission factors in the asymptotic regime: 0.34 (standard deviation of 0.09) kg COIkg soot. However, nonsooting methanelair flames still emitted low levels of CO so that there is a component of CO emissions that is not associated with soot.