Keep-clean device

A purification device for inactivating microorganisms, such as bacteria, germs, mold and/or viruses, present in a gaseous medium, in flowing through the purification device, with an irradiation device—for UV irradiation of the medium, wherein a radiation source is provided in the irradiation device for irradiating the medium and/or the partial flow flowing through the irradiation device, wherein at least one radiation source is provided emitting UV radiation in a wavelength range from 250 to 285 nm,

• wherein a guiding means flow-connected to the irradiation device is provided for supplying a partial flow of the flow of the medium flowing through the purification device to the irradiation device,
• wherein at least one further guiding means is provided for guiding a further partial flow and wherein the further guiding means does not open into the irradiation device and/or is guided past the irradiation device and/or is spatially separated and/or flow-separated from the irradiation device.