A device (1) for manufacturing a three-dimensional object by a layerwise solidification of a building material at positions in the respective layers that correspond to the object is provided. The device comprises a machine frame (2, 3, 4, 5) and a building space (10) that is positioned in the machine frame; an energy source (6) that emits a beam (9) for selectively solidifying the building material; and a ventilator (54) that generates an airflow (T) for cooling the energy source (6). There are provided connecting channels (55), which lead the airflow (T) onto a partition wall (56) that is limiting the building space (10).