Germicidal UV could make airborne diseases as rare as those carried by water

UV causes melanoma which is why we wear sunscreen.

Far UVC?

The article explains this concern in the 3rd and 4th paragraph.

If only 222nm UV lamps didn't cost so much.[1]

[1] https://cybernightmarket.com/products/mini-far-uvc-lights-se...

I have worked on such systems at Signify: There are numerous barriers to wider adoption except for very high risk situations. For instance: there have yet to be lawsuits to determine the risk of exposing people to UV. As you see in the comments below, any "UV" is considered dangerous by people not aware of the biological effects of various wavelenghts.

Besides this, excimer lamps have a low expected lifetime, of both the light source as well as the filter due to the high energy in the UV photons. This makes replacement (and maintenance cost) a real risk. This could be remedied by similar wavelength LEDs from companies like CrystalIS but these are expensive and very low power (only work germicidal on a short distance).

Prof. Brenner at Columbia University has first foreseen applications of 222nm in operating rooms, to prevent infection during surgery.

On the whole, it would need significant investment in both research, certification and risk analysis for this to become commercially viable, so while some of the technology is there, the market demand so far just is not -- post-pandemic.

Still risky, these typical Chinese devices don't come with a filter, so harmful wavelengths will still be present. The filter is actually the expensive part. Also, such a small component would need sufficient cooling as these operate at 4kV. I don't really see this here, so it makes me doubt these devices.

Wong UV wavelength range! 222nm is safe for humans [0]!

[0]: https://www.nature.com/articles/s41598-020-67211-2

Seems like this has potential, but uv exposure is potentially problematic to humans, and definitely problematic to man surfaces and some plants.

Limiting the wavelength helps with humans, but adds a lot of cost.

It might be effective to have a box that draws in air (with a fan, most likely) and the UV source shines within. The inputs and outputs would need to have a few turns and have surface treatments to reduce the amount of uv ligh that can escape. You would have some fan noise though.

Every year our HVAC company tries to sell us UV lights for the HVAC system. They claim it's only about $1500 to install. Are these snake oil?

This is correct and such systems do exist, sometimes combined with sources of ions and HEPA filters. However if you're already drawing air out of the room, it's easier to just filter it with HEPA than dealing with the additional complexity of UV lights (deterioration, energy consumption, replacement).

Mostly used to eliminate or reduce mould growth on the inverter? If HVAC is taking air in or blowing air out, there really wouldn't be a point disinfecting the air.

If it's re-circulating, it could reduce the spread of germs room to room as has been shown during the pandemic in elderly care facilities. That would be the only use-case I see.

they claim it would reduce growths on the coils but also eliminate mold and bacteria spores. Our system is a re-circulating system. One large intake in the center of the house and out flows in individual rooms.

Yeah I saw a lamp for this and it had a proximity sensor to prevent overexposure. There's no way I'm buying a lamp that needs that to be safe. Especially if it's expensive and only lasts a year or two.

The mould reduction is real, and could lenghten the maintenance intervals for cleaning. Not fully eliminate it though, it really only eliminates the parts the UV light reaches (so not the back, or any other part not exposed).

ASTRAL DID IT AGAIN!!!1

No mention of ozone. The more directly dangerous 254nm UV light has the advantage that it doesn't create ozone.

Viruses and bacteria aren't the only bad things you don't want in your air. Ozone is thought to be a carcinogen in its own right and aggravate the health effects of particulate pollution. We want filtering and air circulation anyway, we don't want anything that makes it worse. The consumer electronics industry is all too willing to try to sell us things that make our problems worse, such as ultrasonic humidifiers, or ionizing air purifiers with special chambers for your aromatherapy oils, so it's best to be careful.

Wont micro-organisms quickly adapt and start producing UV resistant strains?

HEPA filters also have deterioration, energy consumption (pressure drop ain't free), and replacement.

HEPA is a mature technology with no big improvement curve, but UV treatment is seeing progress.

Could accumulate in an isolated room, but following normal building ventilation standards, really shouldn't be an issue as shown by Brenner in 2023: https://pubmed.ncbi.nlm.nih.gov/38037431/

There is a giant orb in the sky that emits UV and has for billions of years.

I think the microbes are still trying to figure this one out.

The germicidal effect is a function of the DNA being directly affected by the UV rays and breaking apart. Very few organisms exist that could adapt, this would require external shells, skin etc, not typically found in microorganisms.

Idiotic and massively overlooks/underestimates how complex biology is.

What about beneficial and neutral but important bacteria and viruses? "Air" is actually a complex soup of all types of things. This like applying HCl to a skin infection.

You are correct, however most of the harmful rays get filtered out in the upper atmosphere. Far-UV doesn't reach Earth, only UV-A and small amounts of UV-B (if the ozone layer is more or less intact that is!).

Studying a building's microbiome is really a new field. What happens to people if offices become boxes of sterile air and -surfaces? We don't know.

I also wonder about stuff like this. I think some things are just a bridge-too-far for organisms to evolve protections against. For instance, are we worried about using too much bleach? Or stepping on cockroaches?

I would consider it unlikely that airborne germs form a significant input to our microbiomes.

For example, the gut microbiome is in flux for about the first 3 years of life, and thereafter it's mostly only the relative abundances of different microbes that shift in response to diet, you need something like antibiotics or severe diarrhea to actually induce permanent changes (usually for the worse).

Compared to that, there really aren't many microbes in the air. For children, it could very possibly be bad, but even then I'd expect most of their microbial input to come from their parents, food, and surfaces. Which are already grossly deficient compared to old-school rural settings, but I'm not sure if germicidal UV would make it worse.

Is there any reason why they can't just be installed inside air purifiers/ventilation?

Especially since you could probably get more mileage out of the same amount of light energy by forcing the air through a narrower passage, since only airborne particles are actually going to absorb any energy anyway, and air is mostly just empty air.

> What about beneficial and neutral but important bacteria and viruses?

Such as what? There are some located in the gut, but pretty much everything else out there is in conflict with our immune system.

That solution is actually suggested in the article. However, that still leaves the cost issue mentioned by GP, and until that is solved, this will remain something for specialized applications (operating rooms) and maybe hypochondriac millionaires...

It's a minor point, but it's interesting that they used having AC as a proxy for mechanical ventilation and conclude that it's rare in Europe. At least where I live (NL), mechanical ventilation is common - I think required in some situations - even though AC isn't. It's basically a fancy extractor fan that pumps air outside, so bringing fresh air in. That said, you'd need to reverse that flow to add filters.

I doubt it would be a problem for the microbiome [1] but I would worry about the immune system. Would being inside in sterilized air all the time mean you can't go outside or into a forest without getting really sick?

[1] but who am I, it would still be worthwhile to check obviously

> I think the microbes are still trying to figure this one out.

They mostly figured it out a couple billion years ago. Cyanobacteria oxidized Earth's surface until the atmosphere was flooded with molecular oxigen, that gets turned to ozone in the stratosphere, filtering most UV. Pretty large engineering feat for a bunch of microbes.

Yes, few people have AC but almost everyone living in a semi recent place has mechanical ventilation in, at the very least, kitchen and bathroom, which thanks to physics renew the air of the entire falt/house.

There are radiotrophic fungi that thrive in Chernobyl, so I wouldn't hold too much hope for UV either. It probably won't be able to penetrate a decent biofilm.

article specificaly mentions rooms with poor ventilation. if you have proper ventilation, then you don't need this system in the first place, because you will get ouside air UV sterilised by the sun...

Depends on your HVAC system and the maintenance cost in your area. For me at 150€ per intervention it wouldn't make any sense, but I have heard some HVAC develop a smell and in that case, UV is likely to prevent it.

where are you getting this info?

almost every mucosal surface has commensal bacteria which can provide colonization resistance by other bacteria. lungs, skin, vagina, etc..

too much UV all at once, you mean. melanoma is not common and face and arms - the regions which receive the most sunlight

a moderate amount of UV stimulates vitamin D production, suppresses inflammation, and turns on DNA repair pathways

Interesting, but I use a much more powerful germicidal UV source. Because of the power requirements it uses a fusion energy source located ~150M km away. (sunlight in fresh air.)

In fairness to the article, ventilation was mentioned, but also quickly dismissed. The 60% efficiency figure quoted for ERV is also a bit on the low side for many contexts. And sure, ERV fans themselves use some power (say 50W) but that's about what you'd use in a decent size room with some UV lamps and a fan.

The underlying thought is that outside air (such as a forest) gets UV sterilized by the sun. So this would bring inside air up to the sterilization level of outside air.

there are much simpler and more reliable ways to significantly reduce indoor air contaminents. one is a building method that produces a "floating" slab floor, that has a small gap around most of the walls, and the underfloor space is vented upwards with a chimney, this creates a small but continious air current that removes most dust and other things in the air.

And then the simple expedient of useing radiant heat sources, that while not as lethal as UV, are in fact quite deadly to bacteria and anything tiny with a high water content, but completly harmless to humans and ,animals,plants. Couple this with hard, smooth ,surfaces that are designed so that there no crevices or areas filth can acumulate, useing hard woods,glass,tile,metal,leather/vinyl l,high gloss paint,for surfaces. No cloth, no carpet.While not exactly cosy or friendly, it makes getting home that much nicer. Cheap, reliable, low maintenence, implimentable at scale, now.

This moderate amount of UV is enough to accelerate skin aging which is why we wear sunscreen.

Tardigrades and organisms ables to survive space by having more efficient DNA repair mechanisms.

Unlikely for most organism, true

Your first paragraph is advocating for ventilation, which is great but there's been so much incentive to reduce building energy consumption (heating/cooling) that recirculating, filtration and other technologies have resulted in offices becoming almost sealed off. We are now moving towards more balanced models as people don't feel comfortable in such offices e.g. sick building syndrome.

> things that make our problems worse, such as ultrasonic humidifiers, or ionizing air purifiers

What is bad about these?

...and maybe diy germaphobes.. just like positive air pressure ventilation systems. In fact, you could combine

If I had an HVAC system I would absolutely have UV in it, to mitigate sick building syndrome etc.

Can't comment on the price.

I recently read the book "Invisible Friends," and in it, among other things, the author does go on to explain that it's theorised that many skin infections come from a lack of biodiversity in a persons' skin microbiome, because the "good" or neutral microbes compete with the "bad" for resources. Supposedly people who share a house together often have similar gut microbiomes, too.

So yeah, I don't know. I think you have a point here.

From a quick search, they are not millionaire-level expensive. Here for example is a 20W 222nm lamp that costs $436, with a lifetime of several thousand hours.

https://uv-can.com/products/gerani-far-uv-light?srsltid=AfmB...

Ultrasonic humidifiers require ridiculously clean water. Even regular distilled water is scarcely clean enough. You need to clean the water tank ridiculously well, ridiculously often. No one actually uses an ultrasonic humidifier like it's "supposed" to be used. When the water isn't industrially clean, everything dissolved in it is turned very efficiently into tiny particles. You'll get a fine white mineral dust everywhere.

Ionizing air purifiers make ozone and the makers claim either that it's a good thing or that it's too little to worry about. The first is wrong, the second is a bad sell because the thing it's supposed to be removing is also (by itself) not a big health risk on any single day; the health benefit from removing particles is likely eaten up by the negative health effects of the ozone. You can clean air without ionization, so why? As far as I can tell, it's a pure marketing gimmick, the need to seem high-tech outweighs the actual utility of the thing. (That's also probably why ultrasonic humidifiers are popular, you can see the fog)

I am not convinced that far-UVC is safe for the skin and eyes. I suspect it will cause red spots on skin.

I would rather use it in an enclosed apparatus that has a fan to change its air, but only while measuring the ozone level sensitively.

my description is a bare outline, actusl instalation could easily include a heat exchanger, and by going to radiant heat, it's surfaces that provide the heat,ie: floors (warm/cool feet) and walls, cielings, with humidity controll bieng done in air HCAC is decidedly unsexy engineering, but it can effect, all of every day so worth a bit of attention

I always think of it as the equivalent of inner city youth evolving to be bulletproof

The risk is that they generate ozone, and it's not clear how serious the risks of constant exposure to ozone are.

This is such a good analogy. There are some things that bacteria can evolve to deal with, like training yourself to build up an immunity to iocane powder. There are some things they cant, like training yourself to be bulletproof.

You gotta make sure they install them right. The UV light can degrade the insulation on wires, or break down expensive HEPA or bag filters.

If they put the light in the wrong place it can mess your equipment up.

After years of being a fly on the wall I signed up just to say: most of those things are closer to Radithor than snake oil.

There are only a few companies that sell those things at that price point (installed, $600-$800 for the unit), and they’re all so egregiously fraudulent that I strongly considered doing the leg work for a class action lawsuit.

I got the same pitch a few years ago, but as their bad luck would have it I actually worked on a UV-C LED based germicidal system for years with the same goal in mind, albeit as a hobbyist. My focus was on the LED based variants, which dominates new residential products, so I can’t speak to other systems. That said, regardless of the technology a $1,500 UV-C germicidal HVAC system is a $1,500 MRI machine - no it isn’t.

I was extremely interested in how they managed to accomplish what I had deemed unreasonable with current technology, while also being about 1/4 the cost and 1/15th the power requirements. The latter magic claim is their biggest tell, since the power requirements are slapped on the box and the power supply itself. In this case it was ~17 watts. I’d estimated ~300w for a barely reasonable reduction of common pathogens, and that was based on trying to out-clever systems that used 700w+.

Long story short, I disassembled one of them and they’re regular blue-violet LEDs @ ~405nm, a ceramic fragrance diffuser (popular’ish air freshener in the 90’s) that they marketed as some kind of alien tech UV enhancer, and a high voltage ionizer buried deep in the housing. The last item was going to be my cause for action since they proudly claim zero ozone generation while including a device that is solely intended to produce it. Hilariously I actually had a box of the same ionizers and I think I paid $20 for two scoops of them. I believe they include it so they can technically say the device does indeed have some level of potentially measurable germicidal properties, whereas their purple LEDs would have zero. They never claimed the lights were what did it!

They try bank on a technicality and consumer confusion regarding the LEDs by being very careful to say “UV” on the box, not “UV-C”, and due to inefficiencies of not being a laser the spectral wings of ~405nm purple lights would accidentally qualify as emitting UV. I also think there’s probably a legal loophole that allows the minuscule amount of ozone being generated by the literal ozone generator to qualify as “zero” due to dilution, while still being “germicidal” (if they brush up against the electrodes), so they may be skirting the law there as well. I don’t think the totality of their attempt at legal shenanigans would hold up, but I can’t find any other rational explanation for their very specific design and marketing decisions.

That’s as far as I got with it, since I only had a couple hours to inspect the device, but that was more than enough to make up my mind. Final thought: even if they used enchanted technology that fell from space you may only need to consider the 6-8” wide device being installed directly in the ~18” airflow, and restricting it accordingly, to decide if you’d be happier with an external HEPA filter in a couple rooms instead.

Train yourself, no. Evolve it? Yes. But you'll need an awful lot of generations. Put a robot gun where everything has to come to drink--but it's an air rifle, calibrated to the point of maybe causing injury. Every year you raise the pressure by a tiny bit.

The reason you can't evolve bulletproofness is that it's an overwhelming force. You get evolution when you subject your target to something that only gives a partial kill.

That's not how the immune system works. Practice lets it learn how to fight specific bugs, it doesn't make it stronger overall.

I worked on a 254nm UVC fungicide system at an agricultural robotics startup. For some fungal pests like powdery mildew, there’s growing evidence that irradiating the crops at night (when the fungus has its UV defenses down), can effectively manage fungus outbreaks and save crops yields. This was specifically strawberries.

I had to do a bunch of safety research and testing. We had some grower partners experimenting with it too and they had their workers operate the system without any coverings and everyone got sunburn. Unbelievable.

Another startup working on this right now is TRIC robotics.

Since you seem to have a bit of knowledge here, are there any terms or links you would recommend for a novice to learn more about this floating concept? Really liking everything about this post

Apologies for my weak google-fu

Several thousand hours is not a lot. A year is already 8760 hours.

Sure, I'm not saying it's cheap. I'm just saying there are lots of software developers and whatnot who could keep themselves in UV air filters if they really wanted to.

I can't help picturing the dymaxion house

The topic was melanoma incidence, not skin aging.

But even for skin aging things aren't that simple, though sunscreen companies would love you to think that. UV light is a treatment for psoriasis, eczema, and many other skin conditions.

And vitamin D improves symptoms/reduces incidence of "hypertension, cardiovascular disease, stroke, breast cancer, colorectal cancer, metabolic syndrome, type 2 diabetes, obesity, multiple sclerosis, type 1 diabetes, rheumatoid arthritis, Alzheimer’s disease, autism, schizophrenia, asthma, preterm birth, maternal mortality, myopia and COVID-19" (a lot of these are aging related).

Most studies on UV light/vitamin D supplementation have been done in mice, which are nocturnal and don't get the same benefits as us from sunlight. Here's a recent article in pigs:

UV light exposure versus vitamin D supplementation: A comparison of health benefits and vitamin D metabolism in a pig model

https://www.sciencedirect.com/science/article/pii/S095528632...

Here's a helpful review of the topic:

Are Vitamin D Supplements an Adequate Substitute for Sun Exposure?

https://esmed.org/MRA/mra/article/view/3635

  In this paper we review the current state of the science on this subject and conclude that vitamin D supplements are not an adequate substitute for sun exposure for attenuation of most of these diseases and adverse health effects, particularly hypertension and cardiovascular disease, and should not be recommended in lieu of sun exposure to patients presenting with low levels of serum 25(OH)D. Vitamin D supplementation for such patients could even be harmful, because it will raise patients’ serum 25(OH)D levels, thereby giving patients a false sense of security and obscuring the best available metric for insufficient sun exposure.

The whole idea, along with complete construction techniques was given to me verbaly, and would be stumpted as to where to send you, as my local , venerable {c:1980} passive solar organisation has gone darth, and is somewhat captured by industry, though if prompted still might publish there off grid solar design manual ,which had been adopted by many other organisations worldwide. https://solarns.ca/ The whole idea is based on thermal loops, which is powered, as everything is, by the fact that heat rises, and that internal cavitys/rooms tend to be cooler at the walls, causing a down draft there,and that energy can be put to work.

I know of other instalations in service for decades useing similar methods, but theses ideas and the floating slab are just physics. People are building houses here with double exterior walls acting as thermal breaks, which have no home heating installed, or ever needed, just air/heat exchange,normal domestic activity providing excess heat even @-25°c. Straw bale houses have proven to be the same. Luckily we have a long tradition of challenging building codes and getting engineers behind different ideas, but the full stack of passive technologies is still not bieng implimented at scale.

Ah, that makes sense.

I did not mean to imply at all that the immune system works like that.