Irradiation device for UV irradiation, in particular UV-C irradiation, of a gaseous medium flowing through the irradiation device, in particular air, in particular for inactivating microorganisms present in the medium, such as bacteria, germs, mold and/or viruses, with a housing through which the medium is to flow, having an inlet and an outlet, and at least one radiation source, which is arranged in the interior of the housing and emits UV radiation, for irradiating the medium flowing through the housing, wherein the housing has a reflector, wherein the reflector on the inner side facing the radiation source is at least partially, preferably fully, reflective with a degree of reflection for the UV radiation emitted by the radiation source of at least 0.6, wherein the at least one radiation source is held and/or fixed by means of a holding device, wherein the holding device is connected, preferably detachably, to the housing, wherein the holding device is designed in such a way that the central axis of the at least one radiation source encloses an angle (α) to the central axis of the reflector, wherein a plurality of radiation sources is held and/or fixed to the holding device, wherein the holding device has a first holding unit, the first holding unit being releasably connectable to the housing via a first connecting means of the holding device, wherein the first holding unit has a plurality of first holding means spaced apart from one another at least in regions, wherein the first holding means are designed as, in particular web-shaped, holding arms, wherein the first holding means are connected to a connection area of the first holding unit, wherein the connection area is connected to the connecting means and/or is formed integrally therewith, wherein the radiation source is connected at a front end area to the first holding means, preferably releasably and positively, non-positively and/or frictionally, wherein the first holding means is connected with an end area to the connection area, wherein the first holding means is connected at its free end area to the radiation source, wherein a second holding unit is provided, the second holding unit being connectable, preferably detachably, to the housing via at least one second connecting means of the holding device, the second holding unit having a plurality of second holding means spaced apart from one another at least in regions, preferably designed as, in particular web-shaped, holding arms and wherein the radiation source is connected at a further front end area to the second holding means, preferably releasably and positively, non-positively and/or frictionally. wherein the housing has a reflector, wherein the reflector on the inner side facing the radiation source is at least partially, preferably fully, reflective with a degree of reflection for the UV radiation emitted by the radiation source of at least 0.6, wherein the at least one radiation source is held and/or fixed by means of a holding device, wherein the holding device is connected, preferably detachably, to the housing, wherein the holding device is designed in such a way that the central axis of the at least one radiation source encloses an angle (α) to the central axis of the reflector, wherein a plurality of radiation sources is held and/or fixed to the holding device, wherein the holding device has a first holding unit, the first holding unit being releasably connectable to the housing via a first connecting means of the holding device, wherein the first holding unit has a plurality of first holding means spaced apart from one another at least in regions, wherein the first holding means are designed as, in particular web-shaped, holding arms, wherein the first holding means are connected to a connection area of the first holding unit, wherein the connection area is connected to the connecting means and/or is formed integrally therewith, wherein the radiation source is connected at a front end area to the first holding means, preferably releasably and positively, non-positively and/or frictionally, wherein the first holding means is connected with an end area to the connection area, wherein the first holding means is connected at its free end area to the radiation source, wherein a second holding unit is provided, the second holding unit being connectable, preferably detachably, to the housing via at least one second connecting means of the holding device, the second holding unit having a plurality of second holding means spaced apart from one another at least in regions, preferably designed as, in particular web-shaped, holding arms and wherein the radiation source is connected at a further front end area to the second holding means, preferably releasably and positively, non-positively and/or frictionally.