@acb @cstross I know. I was excited about UV air cleaning as well. LED technology means photons are cheap now, right? (You know where this is headed by now …)

The kind of (high-energy photons) UVC which is effective at neutralizing viral particles is a bit … inconvenient. You can’t just use cheap UV LED technology, for instance: most of the efficient LEDs can only emit lower-energy UVB and UVA.

This means the best / most efficient light sources for UVC are generally vapor-arc lamps, with all the high voltage, glass tubes, and toxic fillings those imply. Plus, arc lamps have a limited service life - like measured in a few thousands of hours - which adds further complications to installing them in ventilation ducts.

So, redux: Powering an arc lamp is less efficient, hotter, and more physically hazardous than powering an LED. And UVC LED tech is still very much not mass-market-ready yet.