(author)

This absolutely depends on the frequency of UVC and the intensity of the lamp. The lamps this post links such as https://aerolamp.net are putting out 222-nm, which is much safer than longer UVC wavelengths and the intensity is well under TLV when placed 8.5ft up (or higher).

See https://www.faruvc.org for more on eye safety.

Ah nice, their data sheet has a spectrum. Kind of odd that they don't market the "we filter out the harmful parts" feature more prominently.

Many manufacturers refuse to post third party spectral assays detailing safety and power output, it's a big problem.

Kinda like advertising "Asbestos-Free Cereal" isn't it? If someone was marketing a product to me and they were super insistent about how super duper safe it was I would probably start getting suspicious

UV rightfully raises concerns about skin damage, highlighting that they're careful about excluding the harmful parts would be helpful for customers who either know just enough to think "UV bad" or to those who wonder how narrow their filters are.

Imo a better analogy would be selling a circular saw with a safety mechanism and hiding the latter in the specsheet.

No, it's more like advertising asbestos-free talc.

They can leak into higher wavelengths. You are really putting a whole lot of trust in manufacturers if you are sitting underneath one of these for decades with unprotected eyes. Not a risk I would take personally (I have glaucoma already, so I'm a bit more sensitive than the average person about eye health)

Far-UVC and Eye Safety: Findings from a 36-Month Study - https://uvmedico.com/news/far-uvc-and-eye-safety - January 16th, 2025

> Far-UVC is a type of ultraviolet light emitted at a 222 nm wavelength that effectively deactivates microorganisms. Unlike traditional UVC light at 254 nm, Far-UVC doesn’t penetrate the outer dead layer of skin or the outer layer of the cornea, making it safe for use around people while maintaining powerful germicidal properties.

> The 222 nm wavelength is unique in its ability to decontaminate without causing harm when used within regulatory limits. Unlike longer UV wavelengths, it interacts only with the outermost layers of the skin and eyes, which naturally renew themselves. This makes it ideal for continuous decontamination in occupied spaces, as confirmed by the 36-month clinical study showing no adverse effects even after daily exposure.

References:

https://www.faruvc.org/ (disclosure: this is published by the same author as this post)

Sugihara K, Kaidzu S, Sasaki M, Ichioka S, Sano I, Hara K, Tanito M. Ocular safety of 222-nm far-ultraviolet-c full-room germicidal irradiation: A 36-month clinical observation. Photochem Photobiol. 2024 Dec 10. https://doi.org/10.1111/php.14052 Epub ahead of print. PMID: 39659140. https://onlinelibrary.wiley.com/doi/10.1111/php.14052

Sugihara K, Kaidzu S, Sasaki M, Tanito M. Interventional human ocular safety experiments for 222-nm far-ultraviolet-C lamp irradiation. Photochem Photobiol. 2024 Aug 19. https://doi.org/10.1111/php.14016 Epub ahead of print. PMID: 39161063. https://onlinelibrary.wiley.com/doi/10.1111/php.14016

Buonanno M, Hashmi R, Petersen CE, Tang Z, Welch D, Shuryak I, Brenner DJ. Wavelength-dependent DNA damage induced by single wavelengths of UV-C radiation (215 to 255 nm) in a human cornea model. Sci Rep. 2025 Jan 2;15(1):252. https://doi.org/10.1038/s41598-024-84196-4 PMID: 39747969; PMCID: PMC11696903. https://www.nature.com/articles/s41598-024-84196-4

I think that blog post is mostly just an AI summary of one or more of those studies.

Noted, it was included for completeness after I had independently found the resources I enumerate.

Interesting study. Only four people though, and the lamps were "carefully calibrated" so exposure was within a safety threshold. I've seen some lamps have safety interlocks that attempt to turn off the light if people get too close. I don't think UVC will be practical for most settings as long as it needs this kind of caution.

If we could establish a higher safety threshold so that we could be sure it wouldn't harm humans even if they were very close to the lamp, that would be great. Then we could deploy it in almost any public or private space.

FYI, all three of the studies are funded by UV light manufacturers: Ushio Inc (first two, 100%), and LumenLabs (last one, partially).

You are not an expert on optical safety and should not make sweeping, generalized statements as though you were.

I am an optical engineer, but don't specialize in eye-safe studies, and I wouldn't dare make a statement without consulting safety guidelines. The eye's sensitivity to wavelengths is exponentially variable, and very specific about some cutoffs - moreso than most biological phenomena, because the limiting factors are bandgaps of molecules, not cell structures.

Retz, I was replying to the same post you were. You were not the problem.

This is not UVC - this is Far UVC and is blocked by the outer layer of your eyeball, so it is safe. https://pmc.ncbi.nlm.nih.gov/articles/PMC10087841/