Abstract: A device for treating a medium using UV radiation includes a treatment chamber to accommodate the medium. An LED UV radiation source provides UV radiation. A chamber-forming structure has a stiffening base structure with at least one orifice formed therein and has a UV-radiation-transmissive film. The base structure defines a placement of the UV-radiation transmissive film. The chamber-forming structure separates the treatment chamber from the LED UV radiation source, and the UV radiation is introduced into the treatment chamber through the chamber-forming structure.