alt Hacker NewsYou Can Just Buy Far-UVC
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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.
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
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.
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.
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...
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-...
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)
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.
> 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.
You can buy UVC LEDs (255nm) for fairly cheap now. $20 or less
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.
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.
Leaving UVC sources exposed to eyesight is completely irresponsible. Please don't do this.
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.