The vent of an oven can be constructed with brick, cast, or steel. Each material has its own advantage depending on the usage. The vent of a pizza oven is usually on its outside, not inside. You can use decorative material to hide the vent from the outside. The vent lets some heat escape the inner chamber/dome. There are two places where vents are placed:
In traditional ovens, the vent is in the front, while in central designs the vent is in the centre of the dome and connects to the chimney to let the heat out. The center vent has the benefit of moving the hot air over the top of the oven and may help improve even heat disbursement. There is another design called "vent in the oven" where the vent is placed inside the oven behind rather than in front of the door.