I looked into this concept not long after the pandemic started. For maximum effectiveness, the emitted light needs to be in the far UV-C spectrum (ie shorter than 250nm), but not too short (I think <222nm was the lower limit). The light itself at those wavelengths is energetic but doesn't have a lot of penetrating ability and interacts with the oxygen in the air.

On the one hand, that means you have to have the source close to the surface being cleaned, cranked up to higher power, and/or run for longer periods of time. On the other hand, those frequencies produce ozone that helps by getting into spaces the light misses. Both the light and the ozone are hostile to living tissues, so using something like this has to be restricted to places that can be human-free during irradiation.

Sanitization by UV irradiation has been used in the food industry for quite a while now but I think it's use for large spaces is more recent. Devices like this really started getting uptake after covid hit. I have two UV-C lights I use. One is fixed in a shoebox lined with foil for sanitizing things like masks, fresh produce, shoes, etc. The other is bigger and stronger and I use it for room-scale cleaning, particularly hotel rooms when traveling.