Abstract: An arrangement for irradiating a liquid with ultraviolet radiation. The arrangement includes a low-pressure mercury lamp placed inside a hermetically sealed housing. In addition, inside the housing a converter or a transformer is provided such that the arrangement may operate from a safe, low supply voltage. The housing further includes a humidity sensor, which switches off the supply voltage as soon as a crack or another leak is detected in the housing. The arrangement may advantageously be incorporated into a shower head or another sanitary provision, when a complete sterilization of the supplied water is desirable.