Ultraviolet (UV) light can inactivate pathogens on surfaces, in the air, and in water. Light-emitting diodes (LEDs) operating in the UVC spectral range at wavelengths below 280 nanometers are gaining importance thanks to rapid advances in efficiency and lifetime. In contrast to conventional UV lamps, they are extremely compact, dimmable, capable of fast switching, and, most importantly, free of mercury. Researchers from the Ferdinand-Braun-Institut (FBH) in Berlin, together with four other institutions, investigated UVC LEDs from 14 manufacturers over a period o…