Abstract: Apparatus for curing the coating of a workpiece (2), which comprises a tank (1) that contains an inert gas heavier than air and into which the workpiece (2) is inserted, and at least one UV-radiation source (4) situated on the exterior (E) of the tank (1) and facing at least one window (3) of the tank (1) to allow the UV radiation to pass through the window (3) towards the interior (I) of the tank (1). To prevent the interior of the tank (1) from overheating and to keep the inert gas atmosphere stable, the apparatus comprises at least one transparent filter (5) disposed between the UV-radiation source (4) and the window (3), where said transparent filter (5) is made of a material that absorbs IR radiation and is transparent to the UV radiation.