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254nm UV is harmful to human eyes and skin, and shouldn't be directly exposed to people. 222nm UV is safe for humans, since the wavelength can't penetrate the outermost layer of skin/cornea. This is discussed at length in the article, so I'm surprised to see this top of the comment page. I suppose it flatters HN readers' view of themselves as smarter than journalists. > “Upper room” UV, the primary form of UV disease control tested to date, is a kind of compromise. The primary wavelength it uses, 254 nanometers, is dangerous to human skin and eyes if directly blasted at them. So, well, you don’t blast it directly at them. The next best thing is to put the lamps high up in a room, where they can kill pathogens at that height and spare the humans. > The problem is that you can’t safely shine conventional 254 nm light at humans, much less at the wounds of humans who are recuperating from surgery. So Brenner and his colleagues, thinking about the donor’s challenge, arrived at the idea of trying out shorter wavelengths, 207 nm or 222 nm far-UV. Those wavelengths penetrate far less than conventional UV, and because of that, far-UV seemed much less likely to damage human skin or eye cells, while still being strong enough to kill viruses and bacteria. |