gas cooking appliances having glass or glass - ceramic plates for cooking surfaces also having gas - radiation burners that are positioned below the plate or atmospheric burners that are recessed in the plate . with gas radiation burners , care must be taken to ensure a thermally advantageous discharge of exhaust gases that are produced and with atmospheric burners , care must be taken to ensure an adequate supply of primary air . accordingly , the glass or glass - ceramic plate forming the cooking surface is partially bent out of the cooking surface plane to form an adhesive - free exhaust air duct or fresh air opening in the bent area . the exhaust air duct and fresh air opening are free of ventilation lattices .