You Can Just Buy Far-UVC | Hacker News Reader

You Can Just Buy Far-UVC

jefftk.com

80 pointssurprisetalk129 comments

Of all the lessons society failed to learn from 2020, the importance of clean air is perhaps the most disappointing.

I wear N95 masks on local trains, long distance trains, planes, buses (most of the time), and movie theaters when busy. The few times I haven’t, in particular local train (unfortunately, lots of unhealthy people) and Amtrak, I have gotten sick - strep and covid. Being sick is in some ways not a big deal, but is serious enough I will keep wearing the masks forever. I get sick far less often than my non mask wearing peers.

The tragedy is that the people operating these services - and schools and hospitals - should have installed filters and UV lamps to make this less unnecessary. At least planes have air circulation, the Amtrak trains are an absolute disaster.

Flu is spreading like wildfire right now. With the advent of these and other technologies, that is essentially an opt-in choice society is making. Totally unnecessary. You don’t have to stop many flu cases before a lamp pays for itself.

We also have found out that Covid decays less quickly in air with high CO2. So highly polluted areas and poorly ventilated ones compound the problem by trapping CO2 in and allowing the virus to survive longer in the air. That is very likely the case for other viruses as well as it impacts the aerosols.

That's really interesting; I had thought it was just the high CO2 was a proxy for greater occupancy, but it does look like there is a physical effect.

https://www.nature.com/articles/s41467-024-47777-5

Yes, it's due to changing the pH of water in the air.

> I wear N95 masks on local trains, long distance trains, planes, buses (most of the time), and movie theaters when busy. The few times I haven’t, in particular local train (unfortunately, lots of unhealthy people) and Amtrak, I have gotten sick - strep and covid. Being sick is in some ways not a big deal, but is serious enough I will keep wearing the masks forever. I get sick far less often than my non mask wearing peers.

I used to get sick when I went into the city. Once I started commuting, it happened a lot less as I built up immunity. I'm not saying everyone should lick doorknobs for maximum health.

Anyways, I got to a lot of shows as well, and wearing masks is joyless. I wear them when I'm feeling sick, to reduce the range of transmission (although I just try and stay home)

That said, for institutions where there are sick and weak people, it's almost criminal that they aren't investing even more heavily in testing these sort of technologies.

> I wear them when I'm feeling sick, to reduce the range of transmission (although I just try and stay home)

I really, really wish more people would do this. If you are feeling sick and need to go out into public, put on a mask. This is doubly true especially if you need to take a plane flight. I understand that you probably can't reschedule your plane flight for a lot of reasons, but, for the love of God, if you're hacking up a lung on an airplane put on a damn mask.

Have some common courtesy.

masks suck. life is risky. but they're a tool and an important one.

> Once I started commuting, it happened a lot less as I built up immunity.

To give another anecdotal evidence: before COVID I used to catch 3 to 4 colds per year. Winter was basically a nightmare season where I was always living in fear of when I would get sick next. After COVID I started wearing an N95 in populated places. As a result, I went to 0 cold per years instead of getting sick even more often because of the additional virus in town. Now I feel I can live normally in winter without always worrying of getting sick and I always feel healthy.

I tried switching to a regular surgical mask (and in general being less careful) to try to find a good middle ground between cost, appearance and protection; while I did not catch colds I did get COVID at the same time as unmasked people around me, so I'm back to N95s (this was likely following something like hours and hours of continuous exposure so makes sense a leaky surgical mask did not prevent it). (my bout of covid was quite mild fortunately; but first time being mild does not mean future ones will be or won't lead to long-term symptoms).

Some people told me that wearing masks will "weaken" my immune system, I still need to see that; after two/three years I just feel healthy and this is refreshing after decades of getting sick all the time.

Plus, instead of the advice of "cook your own food to eat well, sleep well, do sports" that probably requires something like 28 hours per day with a standard-issue job while likely not being as effective as respiratory protection, putting a mask on takes only 30 seconds per day. That's probably good general advice anyway, but not the shortest path to solving the "getting sick often" problem.

I got similar results when i changed 3 things: making sure d levels were around 60, adding glycine and nac supplements and adding a high quality fish oil supplement. My 3 young children have been their usual trainwreck of sickness this winter and inatead of getting sick with them 80 % of the time i have had zero sickness.

i am not here to advertise any of this stuff so i am not going to link or even get the units or amounts right unless i remembered them off the top of my head, just here to point out there are two ways to not get sick: eliminate exposure or increase resistance. For some of us limiting exposure is a painful experience (i cant comfortably wear masks i feel like i am dieing slowly from oxygen deprivation the whole time and the extra moisture gives me a rash eventually)and there does appear to be options on the other path to limit our own sickness.

Does everyone know how often their peers fall sick? I’ve had maybe two illnesses in the last five years and I don’t do all this. In fact, I was masks off as soon as we were allowed to, traveled often via plane and train. I also was at many EDM shows as soon as they opened up.

I used to wear masks whenever I fell sick but it’s been a while. After the pandemic, though, everyone started using these as political symbols and I want to opt out of that personally. A thing I’d been doing for decades is suddenly some kind of statement. I’ve no problem looking out for others but if there’s enough schoolmarming over this, I might just not.

I think people are neurotic about this stuff but probably the reality is that others fall sick often and need to take these precautions and I don’t and therefore see no need to.

At the population level, if it’s worth it, then that’s fine but I think it’s not a given that these things are worth it.

It is a given these things are worth it, as long as they're done properly.

https://www.researchgate.net/figure/Reduction-in-infection-r...

That paper is about mandatory masking and social distancing at the population level. It does not speak to the question of whether it's "worth it" to wear a mask on the train if you're the only one who is doing it.

I used to get sick a lot more often, pretty consistently 3-4 times per year. Since I’ve started masking on trains (specifically because others who are sick and coughing aren’t wearing a mask) and other things (elderberry, zinc, NAC at signs of cold) I’ve gone down to 1-2 times per year. And that is mostly from hooking up with people who had COVID and didn’t realize it.

It’s hard to say exactly what led to the reduction in illnesses, but the N95 masks have the strongest evidence base of the interventions I’ve tried.

ChangeTheAirFoundation.org

I'm confused by the handwaving away of the ozone production. It's well established that ozone is toxic. If these are producing it - and it seems to be agreed upon that they are - that's an obvious issue. The suggestion that "you can just filter it with mechanical air filters (activated carbon)" seems strange because you can just filter viruses with mechanical air filters in that case...

I'm a big fan on the idea of improving air quality/reducing viral load in air to improve health. But I'd really prefer to see more of a push towards the "effective quiet (currently DIY) mechanical air filtration systems" the article links to then a technology with obvious and poorly quantified health risks.

From Aerolamps website:

>Does Aerolamp produce ozone? >Yes - but only a very small amount

>Typical indoor ozone levels are 4-6 parts per billions (ppb), while average levels of outdoor ozone are 20-30 ppb - almost all indoor ozone comes from outdoors. Most likely, you will raise your indoor ozone levels much more by opening a window than by operating a far-UVC lamp.

>It's true that in a sealed chamber in a lab, typical far-UVC installations might produce significant (10s of ppb) ozone. However, our indoor spaces aren't sealed chambers. Both theoretical predictions and experimental evidence suggest that Aerolamp will raise indoor ozone levels by no more than 1-2 ppb. Expected ozone increase can also be simulated with Illuminate.

>However, we recognize that ozone is a pollutant, and recommend that Aerolamp should be used with portable air cleaners which include an activated carbon filter. Studies suggest that a single activated carbon filter is more than sufficient to mitigate any far-UVC derived ozone.

I agree that the filter thing doesn't make sense, but it does not seem like this product would meaningfully increase your ozone exposure.

You can filter viruses with mechanical air filters, but based on the available data, far-UVC can do this much faster than even a high-CADR air filter. The best filter I'm aware of can deliver 200 CFM of clean air quietly or 400 CFM loudly, one high-quality far-UV lamp can deliver the equivalent of ~1000 CFM--silently. That seems like the main advantage to me--plus not taking up the floor space that a large, quiet air filter would require. Basically it's the more dakka solution. But it's recommended to use far-UV with at least one source of mechanical air mixing like an air filter anyway just to make sure its maximally effective

Old-school UVC lights do produce ozone, and it needs to be taken care of.

Newer lights (might) use LEDs that do not produce ozone. I only use LED uvc lights. Also, and this is key: DO NOT look at the uvc light. It can damage your eyes. It is safe for your skin, but it is not safe to look at.

This is incorrect, unless by "old school" UVC lights you mean 172nm xenon lamps. Those produce quite a lot of ozone. 254nm UVC lamps (also quite old school) do not produce ozone.

Ozone is produced at wavelengths below 242nm, but at very low levels. Significant ozone production only ramps up at wavelengths below 200nm (note the log scale in the figure https://onlinelibrary.wiley.com/doi/pdf/10.1111/php.13391) Whether or not the light is produced by an LED is immaterial--what matters is the output spectra.

There are no UVC LEDs that I would consider "safe" for either eyes or skin, except insofar as they are safe because they output very little light, or no UVC at all. SilannaUV makes a 235nm LED, but much of its spectrum is outside the relatively safe "far-UV" band.

Krypton-chloride lamps produce near-monochromatic 222nm, and generally are sold filtered to remove even traces of non-far-UV wavelengths. These are relatively safe because at 222nm, protein absorption in the outer layers of human tissues is so high that the photobiological risk is likely low, especially in skin. I still don't recommend staring directly at those lamps for extended periods of time, especially close up, but this is the only kind of lamp that I might consider 'safe'.

Essentially, if it doesn't produce ozone, it is likely a significant photobiological hazard--unless it's just producing very low levels of light, or not producing UVC at all. Many "UVC" lights you can buy online aren't really UVC at all.

Yes, you can point this specific UV wavelength at your skin and be fine. People have done extensive animal trials and it is not carcinogenic. Many people have been exposed to a lot of far UVC and nothing bad has happened to them.

Looking right at it might not be good for your eyes.

I feel confident for myself that far UVC is safe.

However, the environments I'd want to use this in are those where many people are gathered. I am not sure whether it is respectful/socially good to use this in those situations (given that far UVC products are not subject to any special regulatory review).

Edit for some additional thoughts:

How does this compare to a air filter?

Pros of UV:

- You are helping support R&D for this very important technology

- Even this Aerolamp DevKit is going to be more cost effective at addressing certain pathogens which are highly susceptible to UV, such as COVID. My guesstimate is that the highest capacity/$ off the shelf air purifier you can buy (https://www.cleanairkits.com/products/brisk-box-ultra-black) has about a third to half of the COVID-removing capacity/$ vs. the Aerolamp DevKit. Ditto for energy efficiency.

- Less maintenance vs. an air filter

- Quietest option

Cons of UV:

- Less energy and cost effective at addressing other microbes, particularly mold

- No ability to address dust, another very important air quality issue

- May make others feel uncomfortable

> Yes, you can point this specific UV wavelength at your skin and be fine.

Not so sure about that: there are microbes on our skin, protecting us from harmful bacteria, funghi and viruses. This lamp would kill those friendly microbes.

It seems a better idea is to put this UV lamp in a duct, and treat only the air that passes through.

>This lamp would kill those friendly microbes.

Not really. Those microbes live deep in your pores where the UV wouldn't reach. Even if the UV totally scoured the surface of your skin, it would only be a temporary disruption, which we're generally ok with. After all lots of things disrupt the skin microbiome--showering, hand sanitizer (which DOES penetrate into the pores).

But I think UV skin microbiome disruption is likely to be pretty mild compared to things like eg hand sanitizer. Generally anything that lives on a surface (compared to liquid, and especially air) requires a much higher UV dose to inactivate, because even seemingly-smooth surfaces actually have lots of microscopic nooks and crannies for pathogens to hide in. And skin isn't smooth at all--it's got tons of visible wrinkles and surface complications and complicated geometry. Bacteria are also less sensitive to far-UV than viruses. So lamps that are dose calibrated to kill airborne viruses aren't going to have much of an effect on bacteria that live on a complex surface.

There's actually some data on this although sadly it never ended up published--my lab collected microbiome data for this 66 week hairless mouse skin exposure study https://pmc.ncbi.nlm.nih.gov/articles/PMC9691791/ and found basically no difference in microbiome between the exposed and unexposed mice. It didn't end up in the paper because nobody in the lab had enough bioinformatics expertise to do a nice publishable analysis and just had to take the bioinformatics centers' word on it that there weren't significant differences. Weak/hearsay-ish evidence but not nothing!

In-duct UV is a thing but it's really not ideal for preventing person-to-person disease transmission, for a number of reasons.

> Many people have been exposed to a lot of far UVC and nothing bad has happened to them. > > Looking right at it might not be good for your eyes. > > I feel confident for myself that far UVC is safe.

This is dangerous misinformation. Like any toxic, it's the Dosis that kills

There are very powerful far UVC products available which will give you sunburn on your skin in a couple of seconds

Somebody blasting UVC in a room of people is crypto monkey level of stupid

The person who blasted the crypto people with UV was not using far UVC.

Lots of "toxic" things are beneficial for public health. I'm sure you could poison yourself with soap but we put it in every bathroom.

Like with soap, it does not seem plausible that you could unintentionally harm yourself with far UVC lights.

Ignoring people, what sort of effect does it have on materials (plastics, etc)?

The only studies i can find suggest this is an issue. For example:

https://www.mdpi.com/2076-3417/13/7/4141

  The results of the study showed that far-UVC irradiation causes significant color degradation (∆E00 >5) in all the polymeric materials tested, after 290 J/cm2 radiant exposure. In addition, significant changes in mechanical properties were observed when evaluating elasticity modulus, elongation at ultimate strength, elongation at break, and tensile strength. A particularly large decrease in elongation at break (up to 26%) was observed in fiber-reinforced composite materials.

Is there anything that suggests this will turn out okay?

I don't think "stop using polymers in any place where far-uvc may exist" would fly. So it's cool that we've made something that isn't going to hurt humans, but if it destroys the stuff humans depend on, not sure that works either?

I also don't think the world is going to move to UV-stable polymers for everything just to make far-UVC work (in some cases this isn't even possible). We almost always just make things more UV-resistant instead of UV-stable.

Yes, it may not be good. However, that study used thin material samples - and those are particularly vulnerable to UV. Thicker materials are more resistant because the UV doesn't penetrate into them.

If you want to deploy UV in a specific space (think conference room or hospital ward), I don't think the problem is that hard. There are coatings you can put on top of existing plastics which protect them from UV light. However, I imagine that customer education around managing risk to plastics is going to be a key issue for UV companies if they are to succeed.

This is fair - but i think you are undershooting what is normally thought of as plastics - because it includes most coatings. So the stuff sprayed on your cabinets, rolled onto your floor, paint on walls, etc, are all polymers of various sorts that are not uv stable.

The average dry film thickness of these things is going to be a few mils total (~100% will be 2-6 mils). So very thin.

Pretty much any indoor coating is not going to resist UV well, whether it yellows or not. The acrylic based resins i guess will be okay. The reason all the lights in houses are UV filtered is not entirely about safety - the amount of UV radiation they would produce is fairly miniscule from a human perspective - but if they weren't filtered, leaving the lights on in your kitchen too often would likely, over the course of five years, be really bad for the cabinets, floors, walls, etc.

I think this in practice, the killer. Even if you could deal with plastics themselves, there is just so much you will now have to protect or change.

It's worth noting that the premise of the article- that low cost Far-UVC could not easily be purchased before the Aerolamp, is false.

While AeroLamp has put a proprietary Ushio emitter in a 3D printed enclosure as a sort of reference model to encourage the use of Ushio components, third party tested Far-UVC has been sold for several years now by Nukit222.com at a fraction of the price of any competitor.

Our approach is somewhat different. We use no IP-encumbered components, all parts that can be purchased from any of a dozen Shenzhen factories, we put the product firmly into the Gongkai ecosystem (https://www.bunniestudios.com/blog/2014/from-gongkai-to-open...) without being at the whim of a single high-cost proprietary central component the manufacturer can reprice at anytime.

By focusing on non-IP-encumbered designs that are basically shanzhai-able-"Temu friendly", and then validating the market for those products, you virtually guarantee it will be picked up, copied and improved upon- meaning lower costs and wider distribution.

If you want to make a fit-for-purpose product, faster, cheaper and at larger scale than the Shenzhen Hardware ecosystem iterating at Shenzhen speed with shanzhai- best of luck to you.

The central remaining issue is safety and efficacy, which is why we post all our third party lab tests, for all our products, for download on the sales page. Ozone output, pathogen chamber tests, full spectral assay for safety and power output, UL CE etc. We were the first company to do this, and push for all companies to do the same.

(author)

I'm really glad that you're making and selling far-UVC products. Nukit is the other manufacturer (aside from Aerolamp) that I feature on https://www.faruvc.org

I really hope that your thesis is correct, and we end up with widespread low cost high quality unencumbered far-UVC. In my looking, though, it seems like bulb life is an issue? Is that right, or have I been snookered by Ushio's marketing?

Well, one reason KrCl lamp life became an issue is that they are not replaceable in any commercially available filtered Far-UVC fixture. Currently, at the end of the KrCl excimer lamp life- typically 3000-5000 hours, you throw the entire Far-UVC device away- filters, ballast, control electronics- the whole thing in the trash. There is some talk of possible refurbishment, but at high cost with no companies really in place offering it.

There's really no excuse for this but planned obsolescence. Replaceable light bulbs are 140-year-old legacy tech and trivial to engineer.

Needless to say, this was a major stumbling block for institutional buyers- having to buy and reinstall ~$5000 worth of Far-UVC for a small room every year or two. At which point virtually every Far-UVC company started claiming everything from 5,000 hours to 20,000 hours operating life- with absolutely no data to support this. Some cite in-house testing, but no real evidence is offered.

Given that fraudulent claims in the Far-UVC industry are common, there's every reason not to trust marketing claims that aren't backed by third-party tests. If you don't have a test that proves it, don't say it. (We urge our customers to trust no one, not even us. "Trust" has no place with potentially dangerous UV devices- everything must be third-party lab tested).

A KrCl excimer lamp that could exceed the current, widely documented 3,000-5,000hr (30% degradation or L70) operating life would be huge news and we'd love to see it. But there would be patents, papers, independent lab tests, some paper trail other than manufacturer claims to support this.

Right now, it's all "trust me bro" marketing with perhaps bit of hedging about possibly using reduced power or limited operating time to increase lamp life. By the time buyers have reached 5,000 hours, the products are well out of warranty, and they are left without recourse. If someone says anything about their Far-UVC lasting more than 5,000 hours, the correct response is "Citation?".

In the absence of any credible data showing that anyone is getting an L70 over 5,000 hours of use in the real world at 100% power and uptime, we've chosen to focus on low-cost, non-IP-encumbered, replaceable bulbs, and all of our future products will use them. Any other manufacturer is welcome to use them as well, with the hope that this will get Far-UVC ownership down to the "rice cooker or oscillating fan" price range needed for those in the most desperate need. Because until everyone is protected, no one is. We're all just a cough and a plane ride from each other.

Here is a paper showing that the USHIO care222 module achieves an L70 of at least 10,000 hours: https://www.jstage.jst.go.jp/article/lsj/50/7/50_394/_pdf

Here is a poster with more data in the same series, showing that the L70 is about 13,500 hours: https://cdn.shopify.com/s/files/1/0694/8637/9189/files/24061...

I have never seen any other data for any other commercially available krypton-chloride excimer lamp besides this paper and this poster. All that is "widely documented" is manufacturers claims. The non-USHIO KrCl excimer lamps I have personally tested had L70s closer to 1000 hours, nowhere near 3000-5000 hours. Of course since I am involved in Aerolamp I am not a credible third party, but I am not asking anyone to believe me, I am simply explaining why I decline to believe this 3000-5000 hour claim that is presently without any substantiation whatsoever, not even a paper or conference poster.

Of course, a cheap 1000-hour bulb that is easy to replace and available from multiple manufacturers is great! For many people this approach makes sense. But it is not a 3000-5000 hour bulb and consumers need to know that in order to replace their bulbs in a timely fashion.

You will probably say that the paper and poster and is not credible third party data. This is why Aerolamp has submitted multiple samples to LightLab Allentown for lifetime testing. Perhaps you would be willing to do the same, given how frequently you emphasize the importance of third-party data?

>Here is a paper showing that the USHIO care222 module achieves an L70 of at least 10,000 hours: https://www.jstage.jst.go.jp/article/lsj/50/7/50_394/_pdf

The scientists who wrote this paper work directly for Ushio, correct? And it has not been replicated or verified in any way?

>I am simply explaining why I decline to believe this 3000-5000 hour claim that is presently without any substantiation whatsoever

Very sensible, it should be checked also and claims until then retracted.

>This is why Aerolamp has submitted multiple samples to LightLab Allentown for lifetime testing. Perhaps you would be willing to do the same, given how frequently you emphasize the importance of third-party data?

Sounds like a great idea, we have multiple new gas formulations to test and low-cost replaceable bulbs mean it will be easy to offer customers greater operating life as we improve them. Perhaps Aerolamp would also like to refrain from making any claims without third party data as well? It would be a good example for us to set.

Sure, I'm game! I can loop you into our comms with LLA and you can do the same, and they can send us both the results as they come in. OSLUV says they're happy to pay for it too so no worries about the expense

I really do think the ushio bulb will last 13.5k+ hours though, and that's a long time to wait--how about we publish the LLA results at 1000 hours, and every subsequent 1000 hour interval after that? At minimum, it should give us a sense for how the lamps are performing, even though we might not get the L70 lifetime for a while. Then, as soon as LLA has confirmed receipt of both our samples we can both retract our lifetime claims, at least until the first 1000 hour interval

Just let me know a good email for you and we can get the ball rolling on this, you can get me at vivian@aerolamp.net

Emailed!

I looked it up and Far-UVC (typically 222 nm) seems safe-ish. But how do you confirm it's not outputting 254 nm or other wavelengths in the UVA/B range? Seems likely to happen with sloppy production of sources. You really have to trust the filter on the light or verify the frequency somehow.

(author)

The non-profit OSLUV evaluates lamps and measures their emissions. Here's their evaluation for the Aerolamp, which is the one I've purchased: https://reports.osluv.org/static/assay/aerolamp%20devkit--27...

OSLUV is fantastic; doing great work.

Well, just use your USB spectrometer, of course.

...you do have a USB spectrometer, don't you?

I have mine in my bedside drawer. I use it almost as often as my multimeter.

I need to get one :)

Does yours measure wavelengths that short? A lot of low cost spectrometers don't, because inexpensive glass and plastic optics transmit visible and near-IR radiation but significantly impair shorter UV wavelengths.

Do you have a recommendation for an inexpensive one? I’ve worked with OceanOptics Flame series, but they’re not exactly cheap, and their software was crap.

This isn't (entirely) new. I did the electronics design for this lamp: https://www.fridotechnologies.com (nb: not affiliated any more, no stake in the business, just a freelancer).

The modules and emitters themselves are still relatively expensive - $200+ - but can be bought from China if you want to DIY a solution.

> At $500 this is out of (my) Christmas gift range, but I think we're now at the point where dances, churches, offices, rationalist group houses, schools, etc. should consider them.

One of the things in that list gives this away as something you'd see on HN.

I've built 12V mercury vapor UV-C (254nm) lights for fluorescent mineral hunting, and that wavelength is quite harmful, requiring skin and eye protection. Mercury vapor lamps produce a spectrum of wavelengths, also in the visible spectrum, which gets filtered out since it distracts.

According to this [1] article, the 222nm range is safe for exposure, but the Krypton-Chloride bulb in the far-UVC lamp does also produce harmful wavelengths (256nm), therefore a filter is absolutely necessary. Thankfully simple plastics should work fine for that.

I would still be extremely careful deploying these lights in occupied spaces.

Edit: Come to think of it, filtering the harmful UVC (256nm) from KrCl excimer lamps with acrylic would probably also block the far-UVC. Which makes me wonder what material the filter is. Regular glass stops UVC, which is why UVC lamps are usually quartz or special glass formulations.

"What really needs to be understood is that an unfiltered 222nm Far-UV peak from any KrCl excimer lamp emits a wide band of wavelengths starting at 200nm, past the human safe zone of less than 230nm, all the way to the end of the UVC spectrum at 280nm -- with a very worrisome second harmonic peak at 256nm."

"the 222nm excimer lamp's second harmonic peak at 256nm exclusive to KrCl Far-UVC lights should be treated no different than the well-established carcinogenic hazards involved when using 254nm mercury-line UVC germicidal bulbs."

[1] https://www.prweb.com/releases/222-nm-far-uvc-cancer-risk-wi...

What took me by surprise (but really shouldn’t have) with my set of UV A, B, and C flashlights, is how much of the light can get reflected. Pointing at a rock and seeing a spot on my shirt light up was educational.

The filter is a hafnium oxide interference filter! There are some absorption-based filters being studied in academic settings (as they'd be potentially cheaper to manufacture) but none are used commercially as far as I know

Honestly there aren't that many commercially available unfiltered KrCl lamps out there. I'm only aware of one and it's stupid expensive. Every other lamp you can actually buy is filtered, although some filters are a bit worse than others (though still pretty safe). Any lamp module that uses the Ushio Care222 emitter is certainly very well filtered because Ushio integrates the filter into the module.

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-...

Not the same (less safe)

This is incorrent, we've been selling low-cost Far-UVC for quite a bit longer than Aerolamp (they use some of our technology), and it is is proven to be as safe by third-party testing.

Sorry I will correct my post. I agree with you. Far UVC super safe

The spectra are slightly different, but Nukit is also filtered, I would expect it to be just as safe--just lower output

To correct. Far UVC is super safe ;)

I am not convinced a single lamp placed over the dining table would provide sufficient irradiance to inactivate viruses and other pathogens in the large room. Consider having an infected individual sneeze or cough at the table. The expiration jet would spread so rapidly. This lamp is like a tiny flashlight placed above the dining table. Furthermore, far UV gets absorbed by oxygen in the air. The net irradiance of far uv is worse than 254 nm at a fixed distance from two equivalent (in power and form) sources.

The lamp would be effective if you were able to quickly circulate the air in the room past the lamp.

Yeah, what responsibly deployed far-UV is definitely not is an instant kill beam that immediately inactivates exhaled pathogens. I estimate it takes 100 mW of far-UV about 5 minutes to inactivate 90% of the flu/covid in a 250 sqft room (10 minutes to get to 99%), assuming the air is well-mixed. Far-UV should be thought of as a super-powerful quiet air filter more than anything else--it prevents infectious aerosols from building up in a space, which can matter a lot. You don't necessarily immediately get infected just because someone infected coughed near you--you might only get infected if you spend a long time near them, sharing their air. Continuously cleaning the air prevents these kinds of infections, and can make the infections that do still happen less severe.

You're totally right that circulating the air is important though! Definitely don't use far-UV in totally still air. But you don't necessarily need a LOT of air movement to achieve "good" mixing. Often just an air-change or so of ventilation is enough--just think about what would happen if you started smoking indoors. The smoke would be ~everywhere pretty fast.

The oxygen absorption at 222nm is not significant however--it's enough to produce a bit of ozone (less than you'd get from just opening a window), but not enough to actually absorb a significant amount of radiation. 222nm lamps are generally less powerful than 254nm lamps anyway, but because 254nm is much less safe, those systems have to be deployed in ways that often reduce their efficacy--in special louvred fixtures that kill most of their output or in portable units/ducts that constrain their effectiveness.

222nm seems to be more effective per-photon at inactivating viruses than 254nm too: https://pubs.acs.org/doi/10.1021/acs.est.3c08675

Before buying something like this for my home, I'd need to know:

* Is it safe for babies and small children (whose thin skin and developing eyes might well be much more vulnerable to UVC)

* Is it actually safe for all adults regardless of skin type, colors, dermatologic conditions, or was it only tested on a few healthy college students of one particular ethnicity;

* Does it accelerate degradation of household items, plastics, fabrics, books, and paint; and if so, by how much

Feels like v2 of this will be “ducted” in that it lives next to your air handler and comes on when you are circulating air.

(Like a reef tank sterilizer)

The advantage of far UVC over other UV air cleaning solutions is that it doesn't need to be ducted. This means that you can kill microbes right when they leave someone's mouth - you don't need to wait for them to be sucked through an air handler.

I'm curious if plastics embrittlement is a problem with Far-UVC. I recently was putting a large evaporative humidifier [1] through its paces for someone to get my opinion, and a challenge was that you had to clean the water tank that was the foundation of the unit fairly frequently (every few days). I provided feedback to the manufacturer that a far UVC bulb in the tank might be useful for reducing cleaning intervals.

For use cases where the emissions are contained (HVAC, water tanks, etc), I think it's a slam dunk from an electronic antiseptic perspective. UV is somewhat common in water filtration today, but perhaps an improvement is possible if these bulbs last longer than existing UV solutions.

[1] https://levoit.com/collections/humidifiers-diffusers/product...

(I do not recommend the humidifier by the way, simply too much work to keep the water tank and the evaporation panels clean, I recommend an ultrasonic version instead)

I do not believe that there is a good understanding of the impact of far-uvc on plastic embrittlement.

Delightful, an experiment to be run!

There's research to be done

On the people who are

Still alive.

♫♪

Two studies that I'm aware of, but yeah, data is thin on the ground:

https://www.mdpi.com/2076-3417/13/7/4141 https://www.boeing.cn/cti/downloads/Boeing-Compatibility-of-...

Summarized here, along with other materials considerations: https://blueprintbiosecurity.org/u/2025/06/Blueprint-for-Far...

Along the same lines… where is the proof that as the unit ages it doesn’t leave the magic 220nm range?

It is complete nonsense to point this at people.

Here's a paper: https://www.jstage.jst.go.jp/article/lsj/50/7/50_394/_pdf

This is a study of the Ushio Care222 unit, but its underlying physics is the same as any other KrCl excimer lamp, so its pretty implausible for other KrCl lamps to exhibit spectral drift when this one doesn't.

The spectrum does change a bit over time--it actually gets less dangerous. But it's a very slight difference.

So different hardware, a clinical unit designed for thousands of hours.

Vs a very likely Shenzen unit that a teeny tiny group is selling on a basic website. And, you can make zero claims on whether a light spectrum of a led will go up or down over time despite one example. Amplifiers/voltages, coatings wearing down, oxide layers in diodes breaking down, etc.

I'm not sure what you mean by clinical unit--the ushio care222 is the longest lasting KrCl emitter I'm aware of, but as all bulbs age, they tend to degrade just by losing output, not by spectral shifting.

Basically everyone in far-UVC is a teeny tiny group selling lamps on basic websites, even those who source care222 emitters from USHIO. It's not a big industry!

We don't source our KrCl bulbs from Shenzen, but not for this reason. Yes, that's true about LEDs, but the physics of LEDs and excimer bulbs are different. Excimer spectra don't smoothly shift the way LED spectra do. Excimer spectra have characteristic peaks based on the energy levels of the possible gas molecule species present in the filler gas. The main change over time is the gradual reduction of the 259nm Cl2* peak, which is the main peak of concern--so it fails gracefully. Another possibility is the degradation of the dichroic filter coating under thermal stress--but I've only ever observed this in diffused units, none where the filtered glass is open to the air, and that will happen even on an Ushio bulb.

Nukit is our competitor but I doubt very much that any concerning spectral shift will take place over the course of the lifetime of their lamp.

So… you can’t prove that the unit will not shift wavelength into a harmful range. However, I can prove that by not subjecting myself any others to claimed-harmless light that I can prove it will not become be realized to be harmful.

Cool! You missed peak covid hysteria. But, there are people that will never recover/realize. Like the type of lunatic that would subject everyone to one of these for a thanksgiving dinner in 2025.

You also can't prove that your normal lightbulbs won't magically start outputting harmful wavelengths. Best to live in the dark I suppose.

No, I’m pretty sure that nothing can make a normal bulb start outputting in the carcinogenic range. But, maybe you can explain it to me?

Shrug. Nothing is 'harmless', including far-uv. Going outside in the sunshine isn't harmless. The stove in your kitchen isn't harmless. Can you prove your stove isn't going to explode some day and kill you? No, but you don't expect it to, in part because it complies with consensus product safety standards--germicidal UV products have their own standard, UL8802.

Far-uv is relatively new tech so it's reasonable to be wary, but I'm persuaded on the merits of evidence. Viruses definitely aren't harmless, and I'd rather not be catching random bugs on the regular if I can avoid it, or worry about my grandma catching flu in the hospital. Everyone has to make reasonable tradeoffs about risks and benefits.

It doesn't have to be, but you can avoid any concerns about looking into it or affecting the light quality in the room by doing so.

If you were going to duct it then why wouldn't you just use regular UVC? Much cheaper.

Fair point.

A ducted system seems like it kills a lot of the pros of this system compared to just putting an (effective, i.e. merv-13+) air filter in the ducted system to catch the viruses. And also other things that are bad for you like particles small enough to get where they shouldn't in your lungs.

Ducted UV systems for your HVAC exist now, and don't need to bother with the being UVC since the UV doesn't leave the system.

If I recall correctly my furnace guy quoted me less than $2k for a whole house system that attaches to the air intake on my furnace.

Nah--use 254nm for that. It's a standard thing, if it's contained in a duct it doesn't need to be fancypants human-safe 222nm.

Ducting it kills most of the effectiveness though--now you have to move air through your ducts in order to treat it, so you only get as much treatment as you move air--usually not very fast or else it would be loud and annoying. You can move it faster, but then you need more UV since the faster-moving air won't be exposed for as long. Honestly, upgrade to a MERV-13 filter before thinking about residential in-duct UV

In-room UV is a different story--since it exposes all room air, pathogens start getting inactivated as soon as they're exhaled. The whole room becomes a disinfection reactor.

no way you're supposed to point it down, right?

Aerolamp insists that it's supposed to be pointed directly at "where people will spend time in the room", including tilting it down.

If it's mounted at the recommended 8.5 feet, it's ~impossible/extremely unlikely for the people in the room to get a dose that exceeds the 222nm threshold limit values set by ACGIH (see here https://uvmedico.com/research-and-publications/acgih-2021-th...). You can be standing around in the lamp's hotspot literally all day and still be fine. Check out this sim tool: https://illuminate.osluv.org/?preview_lamp=Aerolamp%20DevKit

But if you're itchy about direct exposure you can also just leave it horizontally on a high shelf or something and it'll still work pretty well. I see lots of people doing that just because they don't feel like buying mounting equipment. It'll just be more dependent on vertical air currents circulating in the room to work well so be super sure that you have a ceiling fan/HVAC/air filter running while using it. Doesn't need much air movement, just a bit, as long as the room air isn't totally still/stuffy.

Yes you are - at the air that may be contaminated.

Kr-Cl excimer lamps (the only cost effective UVC options currently available, and only manufactured via Ushio) have 2 big drawbacks:

1. Very low efficiency ($/watt and lux/watt) compared to UVA/UVB, such that cleaning a conference room between meetings, for example, results in unacceptable dead time compared to normal UV cleaning.

2. 222nm excimer lamps are a known cancer risk (official as of 2022, if I recall correctly), where the issue is that safety limits (in mW/cm^2 per 8 hour day) are based on theoretical skin absorption over a standard workday given a constant dose. Kr-Cl excimers do not produce a continuous illumination, and this intrinsic characteristic worsens with heat load. Transdermal effects are mediated via hair follicles, and shaved skin permits the greatest dose.

Even if you ignore practical safety concerns and take 1950's guidance as gospel, the time to neutralize covid via 222nm will exceed 60 seconds if the target is at the same distance a person would need to be for allowable safety.

tl;dr just put traditional UV in your hvac ductwork and skip on 222nm.

1. UVA/UVB is more efficient in terms of $/watt than 222nm KrCl*, but they're FAR less efficient in terms of germicidal dose than UVC (both 254nm and 222nm). You have to output a LOT of UVA/UVB to kill pathogens at anywhere near the same rate as UVC. I would consider UVA to basically be only "technically" germicidal--it's just not in the same league at all.

2. They're technically considered a cancer risk because UVC is considered "actinic" and so has been grandfathered into that definition, but it actually seems like commonly used UVC wavelengths generally don't penetrate deeply enough into skin to plausibly cause cancer--and you have to keep in mind the difference between 222nm and 254nm. There's definitely no evidence that 222nm is a cancer risk,** but I'm even suspicious of some of the older 254nm studies that report tumors in hairless mice exposed to 254nm. 254nm UVC is produced by low-pressure mercury lamps, and they're *almost* monochromatic, but not quite--they also produce low levels of UVB, which is a serious skin cancer risk even at very low levels (see figure 6 in https://www.tandfonline.com/doi/full/10.1080/10643389.2022.2...). My lab is currently trying to reproduce that result with a filtered/true-monochromatic 254nm lamp and we are just not seeing any tumors in those mice. Those poor bastards are being exposed to such high doses of 254nm that their skin looks super gross, cracked and bleeding, WAY higher doses than anything you'd encounter in a real-world installation--and they're still just not developing tumors. It looks like 254nm is "actinic" in that it's quite unpleasant to experience an overexposure, but it probably doesn't cause cancer, and 222nm seems to not be particularly actinic at all. I get overexposures all the time and basically never notice.

It's also definitely not true that KrCl lamps don't produce continuous illumination. That's exactly what they do!

However, it is true that a typical 222nm installation won't kill covid in 60 seconds. It only reduces it by about 40% in that time period--it'll take about 5 minutes to get to 90% reduction, and 10 minutes to get to 99% reduction. But that is WAY faster than basically any other tech that won't be blowing your hair back, including in-duct UV.

In-duct UV works well for some stuff but not really for person-to-person airborne disease transmission. If it's in the ducts, it's hard to maintain and verify, if the lamps get dusty they stop working (and ducts are super dusty), and anything that goes in the duct only works while your HVAC system is running--and your HVAC system just doesn't run very fast, or else it would be loud as hell. If you're going to put something in your ducts, it should be a MERV-13 filter. Way cheaper, way more maintainable. Then if you want extra air cleaning but don't want to use UV, get portable air filters. I vouch for the reviews at https://housefresh.com/

*although 254nm low pressure mercury lamps are also quite power efficient--about 40% WPE **to be fair, it hasn't been around long enough for long term studies to be done, so if that's your bar for evidence, you'll have to wait--but I think there's other forms of reasonable evidence that can give us information about what's likely a cancer risk and what isn't. The fact that 222nm seems to be >99% absorbed in dead skin cells, and the remaining <1% in non-dividing cells, is pretty strong evidence to me that it's unlikely to cause cancer. Certainly compared to UVB-containing sunlight!*

>Kr-Cl excimer lamps (the only cost effective UVC options currently available, and only manufactured via Ushio)

This is incorrect. Ushio has a patented emitter, but non-IP encumbered Kr-Cl excimer lamps are made and sold in appropriate fixtures at substantially lower cost.

My guess is if we don't get a better vaccine, the COVID issue will probably be mostly or partially solved when 222nm UV-C LEDs become relatively efficient and low cost. At that point they will be mandated in public places.

I don't really think 222nm UVC LEDs are going to be super relevant anytime soon https://www.convergentresearch.org/resources/convergent/soli...

SHG chips might get there but they're very early days right now. And solid state capital economics are pretty unforgiving--I think we'd have to be seeing millions of lamp sales annually for SHG to really compete with KrCl lamps

Honestly, the KrCl lamps currently available are already pretty cheap even at the very small scale they're being sold. If demand picked up I think they could easily fall from $500/lamp to $100/lamp without any serious innovation.

It would be awesome if SHG could beat that and I think it has tons of advantages, but white LEDs got as cheap and efficient as fast as they did because literally everybody needs lightbulbs and they used to consume a lot of energy--general lighting is a huge industry with tons of demand. UVC simply is not.

I hadn't heard about the SHG platform. Thanks for the link!

You can buy UVC LEDs (255nm) for fairly cheap now. $20 or less

This is Far-UVC (typically 222 nm). Regular UVC can cause eye damage.

And skin damage

Evolution has us covered.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3010660/

Yes, however the safety-profile is quite the opposite to 222nm.

https://www.larsonelectronics.com/news/1763

https://uvmedico.com/far-uvc-light

Do you know a good source for finding the latest, most efficient LEDs for DIY projects?

Nichia is pretty top of mind for me as a solid supplier of 265-280 nm LEDs https://led-ld.nichia.co.jp/en/product/uv_top.html. Decently high output, decent lifetime (especially the longer wavelengths). There's also CrystalIS https://www.cisuvc.com/klaran-for-disinfection/ But there's tons

This review paper is from 2019, but it includes a good summary of basically everyone who's relevant to the field https://www.nature.com/articles/s41566-019-0359-9 The author used to keep an updated figure on his website but sadly it seems to be down, or have moved

SilannaUV has 230nm, 235nm and 250nm wavelengths, as far as I know the only supplier that does so https://silannauv.com/

I would be pretty careful with all of these wavelengths though. None of them are truly monochromatic far-UV. Use eye/skin protection when messing with them.

This is an affordable 255nm UVC flashlight (buy filter separately due to US patent bs):

https://convoylight.com/products/gray-c8-uvc-255nm-uvb-310nm

Pretty sure that's a UVB flashlight. There's absolutely no way that anyone is selling 255nm UVC that outputs much of anything for more than a few hours for $45.

A good 280nm chip is ~$100 (https://www.ledsupply.com/leds/uv-c-280nm-nichia-ncsu334a-le...), and it gets exponentially harder to produce shorter wavelengths the further down the spectrum you go. 270nm and 265nm chips are getting there, but 255nm is mostly a research area right now.

that wavelength penetrates the skin. you need to be around 222nm for human safety

uviquity has prototypes of a 220nm solid state chip they’ll commercialize next year (we’re an investor). a single far-uvc photon will destroy the covid virus.

https://uviquity.com/

Cool technology, thanks for posting.

The current state of the art UVC (short wave, e.g. 255nm) LEDs have very low efficiency, compared to UVA (long wave, e.g. 365nm). How efficient are these 220nm solid state chips?

Do they emit other frequencies, or are they monochromatic?

The uviquity 220 nm SHG chips are super cool--they're perfectly monochromatic (though maybe with some blue light leakage) and I hear from their tech lead that they expect to get up to 10% WPE. I think that approach is definitely going to be relevant much sooner than far-UVC LEDs, but they're still early days, it's going to be a long road. Krypton-chloride excimer lamps are more or less the only game in town for commercial far-UV, at least for now.

Full report here if you want more solid state far UV info: https://www.convergentresearch.org/resources/convergent/soli...

It feels like this would backfire.

I mean, UV light is carcinogenic, and environments that are way too clean, are fine for surgery or manufacturing semiconductors, but for most humans (specially children) they can be counter-productive.

The immune system needs something to train on and fight, otherwise you end up with autoimmune diseases and all sorts of crap.

We're essentially walking ecosystems that can easily be imbalanced.

Far UVC is not carcinogenic (most UV is, this is just a specific wavelength that isn't).

Ideally you'd want to use these lamps in environments that our immune systems didn't evolve for, like crowded conference rooms and school classrooms.

Far UVC is carcinogenic when it reaches living tissue. However, it has a very short mean free path so it doesn't, generally, reach the growing layer of skin. It's less obvious whether exposed mucus membranes (lips, nose, tongue) or the eyes are affected. It probably doesn't reach the lens of the eye, which is good.

I think that is the same thing as saying that Far UVC is non-carcinogenic.

I actually read it as saying far UVC is probably carcinogenic for specific areas of your body (lips, maybe eyes).

I don't know if that's true, but it's what GP suggests to me.

Ok… but hear me out…

Hey guys, look you can treat everyone at Thanksgiving with one for $500, and bonus might not be carcinogenic if it is made correctly!

That is not true. It can cause possibly eye irritation but animal trials have shown that it is not carcinogenic even to mucus membranes, eyes, and thin-skinned areas.

There is a small watery layer covering your cornea, this is enough to impede far UV-C (~222nm is safe, 254nm regular UV-C is dangerous to your eye!)

The tear layer only contributes a little bit--far-UV eye safety is mostly down to the fact that the 222nm only penetrates to outer epithelium (so cells that will be dead in a few days anyway), and the fact that your eyes get very little effective dose if you aren't staring directly into the lamp. You've got eyelids, eyelashes, eyebrows, hair, etc, so the effective dose to your eyes is actually much lower than the dose assumed by most safety standards (ANSI/IES 27.1-22, UL8802), which are fairly conservative. Check out this paper http://onlinelibrary.wiley.com/doi/abs/10.1111/php.13671

The best training for immune robustness is going outside and get exposure to a wide range of stuff. But for indoor spaces, air quality is going to be dominated by the microbes and viruses of the people in the space itself. For public spaces and shared residential spaces with poor airflow this would be great - grocery stores, nursing homes, etc. For condos, apartments, SFH, etc. it's probably less necessary, but probably wouldn't hurt. Or nice to have when company comes over, or someone in the house is sick and "polluting" the air.

>> The immune system needs something to train on and fight, otherwise you end up with autoimmune diseases and all sorts of crap.

If you want to train your childrens' immune system, get a dog. Don't intentionally expose them to pathenogenic viruses like COVID or the flu. https://www.science.org/content/article/want-fight-allergies...

Not the same wavelength as UV. This wavelength is blocked by your skin - and outer layer of your eyeballs!

Leaving UVC sources exposed to eyesight is completely irresponsible. Please don't do this.

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).

(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)

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.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10087841/

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/

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