A housing assembly having an integrated baffle plate with a linear drive mechanism is provided. In one embodiment, the housing assembly includes a housing having an inlet and an outlet. A baffle plate is disposed in the housing and is positionable to regulate flow entering the housing through the inlet. A linear drive mechanism is operably coupled to the baffle plate and is adapted to linearly move the baffle plate between positions that are spaced-apart from the housing and a position that closes the inlet. The linear drive mechanism is configured to move the baffle plate linearly without rotating the baffle plate. The linear drive mechanism comprises a gear and a rack connected to the baffle plate, wherein mutually engaged teeth between the gear and the rack are provided with a flat top and grooves for preventing the baffle plate from rotating during the marching of the rack. The linear drive mechanism also comprises a sealing member connected with the periphery of the baffle plate. When the baffle plate is in a closed position, the air tightness at the inlet is ensured through the sealing member.