One thing that is not mentioned (that I saw) is this is very similar to how florescent light tubes work and without florescent material lining the chamber it will spit out quite a bit of UV ...

glass benchtop bioreactor that can be sterilized entirely by UV light. Inside the reactor, four bright LEDs blast every part of the chamber and its instrumentation. The startup is now testing ...

The basic concept of the detector is to build a light-tight test chamber that can be periodically and briefly flooded with UV light, charging up the putatively phosphorescent compounds within.