The flue is the opening that allows the heat or gas to pass through the chimney. If not properly placed, they might release more heat than they should and affect the cooking of the oven. The flue is at the front outside the cooking chamber so the heat circulates within the dome and must pass over the food to escape. If the flue is inside the cooking chamber, the heat will just escape up the flue.
The flues need to be cleaned regularly or they might obstruct the passing of the heat through the oven. It is necessary to use fireproof mortar for jointing the flue liners and the voids between flue linings must be closed with insulating material.