Abstract: Apparatus for curing the coating of a workpiece (1) by means of UV radiation, which is provided with at least one tank (2) of inert gas heavier than air and into which the workpiece (1) is inserted. The apparatus comprises a plenum (3) adjacent to the tank (2), into which inert gas is injected to supply the tank (2) and from which inert gas is injected towards the interior of the tank (2). Between the plenum (3) and the tank (2) there is an intermediate exchange wall (4)that only allows the inert gas to pass towards the tank (2) when a certain level of pressure is exceeded inside the plenum (3). The invention thus allows inert gas to be supplied to the interior of the tank (2) without causing instability or turbulence in it.