A ventilation device, in particular for heating, cooling and/or humidifying air in residential buildings, includes a duct-shaped housing (1) with an air inlet opening (2) and an air outlet opening (3), and a fan impeller (6) as well as a filter unit, heat exchange unit and/or heating coil unit (14) arranged in the main flow direction (Z) of an air flow generated by the fan impeller (6). An air guiding device (17) is arranged in the flow direction (Z) of the air flow in front of a suction nozzle (16)—configured as a flow conditioner, includes a bar structure with air guiding bars-such that a flow inlet opening is configured on the suction side at an axial height in front of the flow inlet opening (15) by the bar structure whose opening surface is smaller than the opening surface of the flow inlet opening (15).