Comment by Animats

There are lots of far-UV germicidal lamps. Here's one, from Shenzhen.[1] (This is Naomi Wu's business.)

There are lot of fake ones out there. Especially ones with LEDs. Nobody has a 222nm LED with enough power for this yet.

Someone should make a simple tester. Something that's on the end of a stick, you hold it up near the ceiling, and it lights up:

- Green - enough 222nm light to be effective, not too much other UV.

- Red - too much other UV, light is dangerous.

- Yellow - only "homeopathic" levels of 222nm, ineffective.

You can buy NBS-traceable UV meters, and even a spectrometer, but they're expensive.

[1] https://cybernightmarket.com/products/nukit-lantern-far-uvc-...