An oven capable of being operated in a self-cleaning cycle wherein the time period of the self clean cycle is responsive to the amount of soil accumulation in the oven. The oven includes a cooking chamber, a heating device for supplying heat into the cooking chamber and an exhaust flue extending from the cooking chamber leading to atmosphere. A heat control device is provided for controlling the operation of the heating device and an input device is used for signaling the heat control device to initiate the self-cleaning cycle. A gas sensor communicates with the exhaust flue for measuring a concentration of a gas component produced from combustion of food soils within the cooking chamber. The gas sensor has a signal output indicative of the measured concentration of the gas component during the self-cleaning cycle. The heat control device receives successive gas concentration signals from the gas sensor and calculates a gas concentration versus time curve. The heat control further calculates a gas concentration area representing the area under the gas concentration curve, and terminates the self-cleaning cycle in correspondence with the gas concentration area. The heat control device may further determine the peak gas concentration or the slope of the gas concentration curve for a period of time and terminate the self cleaning cycle in correspondence with the calculated gas concentration area and the peak gas concentration value and/or the calculated slope value.