How long does it take to kill germs?
There is no valid universal duration to inactivate germs, since the essential factors such as performance of the UVC source, the lethal dosage of the microbes and the roomspace conditions vary individually. Only when all this data is known, it will be possible to define reliable predictions about inactivation time.
It is central to understand that the UVC disinfection technology is subject to the dosage principle (duration x radiation intensity). The further away the UVC source, the weaker the intensity of the radiation and thus the longer the irradiation time has to be to get an effect. In close proximity, you can reliably disinfect within the shortest duration (parts of a second).