I expect that far-UVC (222nm) light will play a part in making indoor air safer to breathe.

For those unfamiliar, UVC kills microorganisms (both bacteria and viruses - although there's some debate over viruses being 'alive', so maybe 'kills' isn't the right word).

UVC is common in indoor bio lab spaces where an airborne microorganism might spoil an experiment - but UVC can give you a nasty burn (sunburn on the skin, something like snow-blindness on the cornea) - so the lamps are in shielded cabinets and fans are used to move the air through past the lamps.

Enter far-UVC. Still as deadly (or whatever the word should be) to microorganisms, but, the higher frequency cannot get past the top layer of our skin or the layer of tears over our eyes - so they're safe to use in public spaces..

Currently, lamps that can output 222nm far-UVC are quite expensive, but as more are produced, the price should fall (look at historical prices on LED lamps). Even at current prices, adding coverage to indoor spaces would be considerably cheaper than retrofitting ventilation, particularly if that ventilation includes heat recovery exchangers or if major work is needed to retrofit larger ducting. And for high-traffic small enclosed spaces, like elevator cars, they're a no-brainer.