It does work on air. Some commercial HVAC systems integrate UVC lamps. It needs relatively high power or a long straight run where the air flow and light are both pointed in the same direction.
Yup. You can even buy them for home AC systems. Both of our AC units include UV lamps, and we bought them years ago. And they include whole-home HEPA filters, too.
And our room IQAir HyperHEPA filter units go down to 0.003 microns, which is an order of magnitude smaller than virus particles.
But that only helps you at home, and it only helps you with those particles it captures before you breathe that air. If you’re between the air filter and the virus particles in question, then you’re more likely to be the filter that catches those particles.
https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradia...