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.
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 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.
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.
https://www.researchgate.net/figure/Reduction-in-infection-r...
TWO YEARS (not to mention a trillion and a half usd and eur) wasted on "handwashing" against an airborne virus plus all the other crap that came along with this betrayal or was it utter stupidity I still cant tell which.
Our Public Transports AC is so shit, that in a hot summer, the outside is cooler than the full SBahn.
And a single Car! Had such a good air filter in comparision.
I primarily communte by car now after the office moved and i'm def less often sick.
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.
>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.
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
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.
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.
The modules and emitters themselves are still relatively expensive - $200+ - but can be bought from China if you want to DIY a solution.
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...
...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.
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...
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 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-...
(Like a reef tank sterilizer)
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.
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)
On the people who are
Still alive.
♫♪
It is complete nonsense to point this at people.
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.
If I recall correctly my furnace guy quoted me less than $2k for a whole house system that attaches to the air intake on my furnace.
1. Very low efficiency ($/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.
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.
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!*
One of the things in that list gives this away as something you'd see on HN.
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.
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.
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?
Full report here if you want more solid state far UV info: https://www.convergentresearch.org/resources/convergent/soli...
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.
https://convoylight.com/products/gray-c8-uvc-255nm-uvb-310nm
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.
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 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.
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...
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.
I don't know if that's true, but it's what GP suggests to me.
Hey guys, look you can treat everyone at Thanksgiving with one for $500, and bonus might not be carcinogenic if it is made correctly!
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.
> 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
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.
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.