The flue and the vent are vital part of a pizza oven especially the wood fired types. The function of the vent is to allow for excess heat and gasses to leave the oven compartment. To function appropriately, the flue has to be of a given size. According to experts, the diameter of the flue should be 15 cm to 20 cm. the vent can vary in height but it should be long enough to allow for safe removal of the gasses above the normal human height – 3M from the ground is appropriate.
That said and done, the placement of the flue on the oven is crucial. Placement can be done as to cause poor cooking of the oven due to too much loose of heat. The flue should be placed outside the oven after the entry door.
Further information: Wood fired pizza oven flue, How to build a pizza oven flue, and How to build a pizza oven