The paper describes the main mechanisms of NOx formation (thermal, prompt NOx and through N2O). It is shown that, for combustion products when the gas temperature is less than 1650 K (Tgas<1650 K), the residence time has a weak influence on NOx formation. A concept for the simultaneous reduction of NOx and CO in low-emission combustors with large residence time is suggested. Some methods to organize an operation process with low NOx and CO formation are suggested as well. The low-emission combustor configuration is presented. The paper describes both the experimental results of investigated model combustors and investigations of a low-emission combustor designed for mid power gas turbines, developed with the suggested operating process mechanism.