A vestibule for use with a microwave oven having a conveyor mechanism passing there-through is designed to prevent microwave radiation from escaping to the surrounding atmosphere. The vestibule includes a choke region and a paddlewheel region with a trap region located directly there-between. The choke region includes a series of quarter wave choke networks or devices and the trap region includes a body having quarter wave chokes with microwave absorbent materials disposed therein which absorb microwave radiation that has passed through the choke region. The paddlewheel region includes at least two pairs of paddlewheels that are synchronized with the conveyor mechanism and each other to permit individual products to enter an open end of the vestibule while preventing microwave radiation from escaping therefrom. The paddlewheels are synchronized such that while one pair of paddlewheels is in an open state, the other pair is in the closed state.
