A cover plate device for a heat exchanger device, especially for a vehicle heater, includes a receiving zone (14) intended to be arranged on the heat exchanger device and to receive a fluid stream leaving the heat exchanger device in a first direction of flow (S₁), a mixing zone (22) for mixing the partial fluid streams (F₁, F₂, F₃) leaving the heat exchanger device in different areas and entering the receiving zone (14), and at least two delivery zones (24, 26) for delivering the fluid stream leaving the mixing zone (22) from the cover plate device (10).