The gaseous emissions of carbon monoxide, nitric oxide and unburned hydrocarbons have been measured in the exhaust of a small industrial gas turbine engine. Using a rate limited partial equilibrium approach, the mechanisms responsible for excessive carbon monoxide concentrations are studied for the entire turbine power range. A simple model is formulated from these mechanisms which yields reasonable agreement with measured values and predicts the CO emissions variation with load. It is shown that excessive CO emissions are caused by the rapid quenching of primary zone combustion gas by the dilution air jets. At the jet interfaces, a fraction of the gas contains CO concentrations far above equilibrium. A contributing factor to excessive CO emissions is the poor fuel distribution in the primary zone. Where fuel burns with air at an equivalence ratio less than 0.6, some of the CO formed by rapid partial oxidation of the fuel remains throughout the engine. Minimum CO emission rates from the industrial gas turbine engine studied would be obtained by burning a uniform mixture of fuel and air in the primary zone at an equivalence ratio of 0.7.