An oven comprising: a cooking chamber configured to receive a food prouct; and an air circulation system configured to provide heated air into the cooking chamber , wherein the air circulation system comprises an air cleaning system , the air cleaning system comprising: a catalytic converter configured to clean air in the air circulation system; an input array comprising perforations through which cleaned air that has been processed by the catalytic converter is provided into the cooking chamber ; and a preheater disposed proximate to the cooking chamber to use heat generated by the cooking chamber to preheat the cleaned air prior to entry of the cleaned air into the cooking chamber through the input array , characterized in that the cooking chamber comprises a top wall forming a heat exchanger surface at an interface between the preheater and the cooking chamber , wherein the input array is spaced apart from a back wall of the cooking chamber by a distance, and wherein the heat exchanger surface extends from the back wall to the input array along the top wall of the cooking chamber to traverse the distance between the input array and the back wall. a cooking chamber configured to receive a food prouct; and an air circulation system configured to provide heated air into the cooking chamber , wherein the air circulation system comprises an air cleaning system , the air cleaning system comprising: a catalytic converter configured to clean air in the air circulation system; an input array comprising perforations through which cleaned air that has been processed by the catalytic converter is provided into the cooking chamber ; and a preheater disposed proximate to the cooking chamber to use heat generated by the cooking chamber to preheat the cleaned air prior to entry of the cleaned air into the cooking chamber through the input array , characterized in that the cooking chamber comprises a top wall forming a heat exchanger surface at an interface between the preheater and the cooking chamber , wherein the input array is spaced apart from a back wall of the cooking chamber by a distance, and wherein the heat exchanger surface extends from the back wall to the input array along the top wall of the cooking chamber to traverse the distance between the input array and the back wall. a catalytic converter configured to clean air in the air circulation system; an input array comprising perforations through which cleaned air that has been processed by the catalytic converter is provided into the cooking chamber ; and a preheater disposed proximate to the cooking chamber to use heat generated by the cooking chamber to preheat the cleaned air prior to entry of the cleaned air into the cooking chamber through the input array , characterized in that the cooking chamber comprises a top wall forming a heat exchanger surface at an interface between the preheater and the cooking chamber , wherein the input array is spaced apart from a back wall of the cooking chamber by a distance, and wherein the heat exchanger surface extends from the back wall to the input array along the top wall of the cooking chamber to traverse the distance between the input array and the back wall. <EOS>