A couple of months ago I mentioned "Far UV" as a possible solution to COVID-19, so I was interested to see it mentioned prominently in a recent tweet thread from an expert.
In general, the thread was about which engineering (not social) measures are worthwhile and which aren't. To summarize super briefly, his advice is: Don't waste time with cleaning, but do spend time on ventilation. Here are his top four recommendations:
4. Open windows. Also open the door and use a fan to push air from the window and out the door. It will be a lot of flow. The main problem is it can't be done when it's cold outside. It's difficult to calculate the exact flow from windows. 17/21
3. Ventilation Improvements. Good ventilation can provide between 3-6 ACH. All the previously mentioned strategies are inferior to having a building with good ventilation. I can't overstate the importance of investing in upgrading ventilation. 18/21
2. Upper Room UVGI — the real deal. It can add 12-24 eACH. It reduced measles outbreaks by 75%. If we want to go all out on mitigating airborne spread, this technology is needed. 19/21
1. Far UV. I've seen estimates between 10-300+ eACH. This technology isn't widespread yet and still expensive, but it could be a game changer moving forward. 20/21
Note that ACH stands for air changes per hour—or the equivalent. Ventilation is good, and it's something we should focus on in the short term, but various forms of UV radiation, either in rooms or in ducts, have the potential to be spectacular. Why aren't we pouring billions of dollars into investigating this stuff? It's not as if COVID is the only thing it works on. Monkeypox, anyone?
NOTE: Here in California we've spent billions earthquake proofing our infrastructure. Why don't we do the same for virus proofing?
Far UV is ionizing radiation and a carcinogen. It needs to be incorporated into ventilation systems such that no direct exposure occurs to occupants. This is not at all like the test setup illustrated.
From the article Kevin cites and my own googling, that does not appear to be the case:
https://meridian.allenpress.com/radiation-research/article/187/4/493/192663/Germicidal-Efficacy-and-Mammalian-Skin-Safety-of
https://www.nature.com/articles/s41598-022-08462-z
https://www.nature.com/articles/s41598-020-67211-2
OTOH, I'm no expert. This is just from a quick search. Do you have evidence/cites to back up your claim?
Depends on the band and the claim.
And it doesn't just kill pathogens, it destroys art and pigments and plastics.
Mercury germicidal lamps usually work at the 254nm wavelength, which is longer than the 122-200nm range that is called "far UV." Even excimer lamps for germicidal use are around 220nm, as in the reference you provide. Neither is energetic enough to make ozone. 220nm may be safer for a given irradiance since it is stopped at the other (dead) layer of skin, but one study with a skin model and a few naked mice isn't nearly enough to say so.
Far UV is not ionizing radiation. As for a carcinogen, like all toxic exposures, the dose makes the poison:
"This reduction was achieved using Far-UVC irradiances consistent with current American Conference of Governmental Industrial Hygienists threshold limit values for skin for a continuous 8-h exposure."
https://www.nature.com/articles/s41598-022-08462-z.pdf
"Far-UVC" isn't "Far-UV". Much of the Far-UV band is energetic enough to make ozone -- in fact mercury lamps with fused quartz envelopes are used to do just that, since the 185nm Hg line can ionize the oxygen in the air to make ozone. This finds use in water sterilization, etc.
It's arbitrary, I know -- given that UV-C is 200–280nm I can see how 222nm is "Far-UVC." But "Far-UV" is 122-200nm. Two different nomenclatures, I guess. (The weird 122nm value is from the 121.6nm Lyman-alpha line of hydrogen and right around 10eV of photon energy; above this energy/below this wavelength is "Extreme UV", which goes right up to X-rays.)
I'm going with the Nature link: 222 nm.
UVC has a wavelength of 200 to 280 nm, but the sterilizing lamps seem to run at 254 nm, just a bit too long a wavelength to produce ozone (100 - 249 nm). I suspect one could still get a sunburn though.
Yup. As I noted elsewhere I think there is some confusion as to just what "Far UV" is. The thread Kevin points to references 222nm excimer lamps, which are not Far UV but are at the far end of UVC. It is claimed these are in the sweet spot where the outer layer of skin blocks the UV radiation, preventing the damage that longer UV wavelengths can cause. This may well be so, but it needs more than a couple research studies before we go putting them everywhere.
Not convinced that ventilation will be enough to stop the more virulent strains we have now. I caught COVID after spending several hours in a small office with one other person. We had two windows open on both sides of the room so there was a continual flow of air - you could feel the breeze. The person who gave it to me was wearing a K95 mask the entire time. Thinking back I wonder if the ventilation was actually sweeping the virus towards me due to the configuration of the windows. Not sure how you can arrange ventilation so that someone isn't downstream of other people.
First, sorry you got it in that situation. That really sucks. My sympathies.
Second, KN95 masks help. N95s are slightly better. Either needs to be properly fitted and worn correctly. But neither (and nothing) is a 100% guarantee of safety.
Lastly, re your ventilation question: If it's just two people, draw a line between 'em. Airflow should be perpendicular to that line. In the situation you described, assuming you were face-to-face or pointing the same way as the other person, you should have felt that breeze on one side. It gets more complicated with more people the closer they're packed. That's where the UV disinfection could be helpful.
You mean perpendicular to a line drawn from one to the other? “Between them” implies a line dividing them.
Sure, but that is impossible with the configuration of the office and the windows, plus the direction of flow would depend on the wind direction, which changes a lot. We'd have to rearrange the office furniture depending on the wind direction. Frankly, with the current variants I think it is basically hopeless unless you isolate. COVID has just ripped through every single employee and associates now. Luckily none of us has been seriously ill and we were all vaccinated and boosted. I'm trying to avoid indoor gatherings whenever possible.
It has been shown that when the air flow is lateral (like in Kevin's sketch) then the virus can be carried from person to person. This happened in a restaurant with ventilated air blowing across the room.
My suggestion is to enlist the aid of the engineers who design semiconductor fabs to engineer the airflow in a room. It should be top to bottom, not across. The air pulled from the floor level is pushed through a scrubber.
A scrubber is sort of an active filter. It is a small box filled with something that provides huge surface are; think nested whiffle balls. Water is continually sprayed in this box. All particulates, of any size, are trapped in the water. You could use high intensity, short wavelength here to kill anything.
This is not high tech. It could consist of some cardboard tubing, a water tight box and a fan.
I'll bet if we had a national competition some clever engineers could find a way to make this cheaply with readily available materials. The key would be to do it correctly.
As a bonus this cleans the air of pollen, mold, dust and other irritants that affect those with asthma or allergies.
Nope, you mean contagious. It's becoming less virulent all the time.
There's no evidence for that.
Please don't feed the troll. It only leaves its droppings to get attention. Starve the troll.
Yes there is. If your this stupid, you should kill yourself.
So you were exposed to someone all day?
You don't think duration might have had something to do with this?
Or that the air from their desk was going to yours before going out the window?
Uh, those recommendations could very well serve as an illustrative joke on how clueless engineers can be.
Open windows? In how many offices, other workplaces, stores and theatres and other public places, and many apartments is that even possible? And, even where one can control the windows, opening them in bad weather, or in noisy neighborhoods, or in other circumstances is not realistic.
All the other stuff? Some has been proven not to work. Others of the suggestions cost quite a bit of money which many individuals could not afford, and many landlords and corporations would refuse to install.
What on this list has proven to not reduce exposure?
Kevin
One of your worst posts. You have the excuse of being on vacation, though.
Air can be treated so long is it's confined into a small space. The air handling equipment is such a space and the air could be treated within that machine but it's not technologically feasible yet. But, this also brings to mind the difference between being outside in natural ventilation, and being inside where air is deliberately moved,
In buildings the decades old mantra was heat it (air) and cool it as efficiently as possible. You MOVE the air from point(s) A feed line to point(s) B return line. The problem is that air movement has to go THROUGH other peoples breathing zones - so anyone who is currently spreading COVID will be aided by the very system designed to kill the germs !!! This is the DANGER of putting many people in confined areas. Planes, and cruise lines (as examples) have people crammed into those spaces. The same holds true for a call center where employees sit side, by side, by side. Meat packing plants where people are elbow to elbow.
Take those people OUT of their confined space and put them outside and the germs spreads gets diluted by the "infinity" of the space. An 8ft wide, by 10 ft long by 8 ft tall room contains 6400 cubic feet of air. Put 6 people in that room and all would get sick, should someone have COVID. Put those same 6 people in the outside with a gentle breeze and infinite cubic footage the only people who "may" get sick are those down wind from the sick person. There are other factors of course like outside heat or cold etc but dilution of the germs outside happens MUCH more quickly that it does INSIDE.
Besides, if COVID is endemic why should we spend the money? It only affects old people anyway. If hundreds of kids dying in school shootings isn't enough to warrant new gun laws I guess old people who were close to dying aren't worth investing in either - according to republicans
"It only affects old people anyway"
Sigh, google "Long Covid".
Citizen
I GET it.
Long COVID is a little different than original COVID.
I shoulda put a "snark" moniker on that part of my comment to reflect the fact that I was parroting our anti-semitic, racist troll - who's main claim to fame is being the BEST goal post mover I've ever seen !! "It will be over when school opens", Then it was "It will be over by Thanksgiving" - which morphed into "It will be over by Christmas - THEN Easter".............
And TRUTH be told long COVID is worthy of a post or 2 by Drum. What is it? 1 in 5? (20%) develop long COVID?
We need to control the spread of normal COVID first and foremost just to slow down the mutation rate of this disease
Another victim of Poe's law.
Not so much now. Long Covid ended with Delta.
There is more and more evidence that Long Covid is a psychological condition that may not even be caused by Covid.
There is almost no correlation between claims of Long Covid and biomarkers for illness like inflammation. There is a strong correlation between claims of Long Covid and previous mental health treatment / counselling.
Link, please.
Here's mine:
https://www.nature.com/articles/s41575-022-00611-z
Complete lack of sources (as usual) duly noted.
Your point seems to be that being outdoors is better being indoors and that having people distanced is better than having people together. Both of those are true, but there are plenty of situations where it's not practical to have people outdoors and/or distanced. Contra your claim, properly designed ventilation does not aid in spreading COVID-19. And the UV treatment that's the main focus of Kevin's piece (and that you more or less ignored) certainly does not spread it.
UV treatment is used in hospitals to sanitize rooms but it is extremely expensive.
Air movement within a confined area does IN FACT spread covid as the air has to move either down to floor returns, up to ceiling returns or across the room to wall returns which brings the air right past a person's breathing zone. It's the reason why "clean rooms" used in semi conductor manufacturing use floor returns. It is far more efficient in a temperature controlled environment to push cold air into a room from the ceiling while your floor vents suck the air out of the room - but even that pulls the air right through the breathing zone of anyone in that room
Outside there are NO CONFINES to the air movement. It goes along with the old saying dilution is the solution to pollution - which is why we STILL dump trash in our oceans !!!
In the case of COVID we would be far better off with medicinal efforts rather than mechanical efforts in our attempts to stop the spread, because the disease is changing. What passed for Wuhan two years ago is no longer recognized when compared to Omicron.
UV-C - the spectrum that kills viruses and bacteria is absorbed by our atmosphere and has to be created mechanically to be of any useful purpose at ground level. You CAN do it in an air handler but it's not very efficient. The more people you have in a confined area the more you have to treat the air, 5,000 people on a cruise, 2500 in a meat packing plant, or 2000 in a call center make for a very challenging environments - never mind 250 on a plane, or 30 people on a bus
Although commercial air transports package a lot of people in small volumes, Covid-19 transmission has proved surprisingly low. The ventilation systems maintain ceiling-to-floor airflow, and are equipped with HEPA filters. I would presume that many or most building HVAC systems incorporate filters which at least have the potential to be upgraded to HEPA, if the pressure drop doesn’t increase too much. Assuring minus-Z flow would be more of a challenge if not already the case.
“Why aren't we pouring billions of dollars into investigating this stuff?”
Did you just move to this country? It’s like you’ve not been living here your whole life.
(1) We have 1 of our 2 political parties - the one with a structural advantage in elections - that is anti science. Climate change is a myth. The earth is only 5000 years old and humans coexisted with dinosaurs. Homosexuality is a choice and has not been documented in hundreds of species. Masks and vaccines are a crock. The list goes on and on. And so you expect science to win out in Congress on the need to fund future plague mitigation and avoidance?!
(2) That same political party also loathes new spending (if it’s not somehow related to the military) and hates - with the intensity of a thousand suns - the idea that taxes might have to go up for any reason. So even as a plague is raging on right now, they don’t want to fund anything to mitigate it right now. They voted against all efforts to extend Covid coverage this year even as cases rise again and people are still dying here faster than they are in any other advanced nation.
(3) As others have mentioned, that same political party also has become a death cult. They celebrate our country letting millions of people die of Covid, women die from ectopic pregnancies, poor people die from lack of health insurance, minorities die from cops shooting them even while unarmed. They won’t let the other political party do anything to stop any of those problems going on right now, and defund anything that does manage to slip through during the rare periods when Dems are allowed to govern. (Remember how “volcano monitoring” was deemed stupid?) Why would anybody expect them to allow Democrats to deal with future problems like the next pandemic?
Seriously Kevin - open your eyes to what the GOP has become.
and hates - with the intensity of a thousand suns - the idea that taxes might have to go up for any reason. So even as a plague is raging on right now, they don’t want to fund anything to mitigate it right now
In general Republicans hate taxes, yet. But I don't think you're giving them their due as to why they'd surely oppose an initiative to improve our anti-pandemic infrastructure. The reason certainly isn't that they're worried about new spending. Rather, they oppose doing anything to help or improve the country.*
*Because that might help Democrats, who currently own the incumbency brand.
They did nothing for the 99% when they were the incumbents; though at least they failed to take away health insurance from millions. Because, if you’re not already wealthy and you need help with any aspect of life, it’s because God is punishing you for being a bad/lazy person, and we don’t want to go against His* will.
*we all know He’s male, of course.
Why aren't we spending money on this? It's quite simple -- life is cheap in America.
One million are dead from covid; perhaps more than that are dead from opioid abuse; mass shootings -- including the slaughter of children -- have become commonplace and collectively we shrug our shoulders and go on our way.
Um, monkeypox is spread via physical contact no? …
yes in the main, but it also can be spread through the air. the handful of case in this country so fair have been through physical contact. i think the point is that there are and will be diseases beyond covid that do/will pose threats to our health.
As others have pointed out, you can't expose people to intense UV radiation for long periods of time. Aside from that, high intensity UV lamps are expensive and they don't last very long. The one in our water purification system needs to be replaced every year. It's not just a one time expense, it is an annual huge expense.
I was assuming Kevin meant UV treatment of the circulated air within the duct, which wouldn't expose building occupants at all.
Not all UV is the same.
"This reduction was achieved using Far-UVC irradiances consistent with current American Conference of Governmental Industrial Hygienists threshold limit values for skin for a continuous 8-h exposure."
https://www.nature.com/articles/s41598-022-08462-z.pdf
If we spend all that money on ventilation we won't have enough money to post a police officer in each classroom!!!!!
Not really....
Power supplies, ozone generation, surface damage, irradiation time, etc. all have to be addressed. Leave a fingerprint on a surface then shine UVC light on it and see what happens (never leave a fingerprint on the light source!). Ozone generation is less of a problem with some of the newer lamps, but other issues still need to be addressed, especially if a home unit is being installed.
Some of this has already been deployed in some institutions. A placed design to use UV disinfection with trained staff should be ok. Sticking a germicidal lamp in a classroom is not.
https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation/uvgi.html
Speaking as a long-time Building Engineer, and nowadays Engineering Manager, Increasing ventilation is something that should be easy, but often is not. There are practical upper limits on fan through-put of existing systems, and the cost to condition the air can get quite high.
That said, this is really a cheap investment. Using the earthquake hardening analogy is pretty spot on. We just have to re-calibrate our priorities a bit. Increased ventilation helps with many things., it just costs more power and money
As far as UV systems, as others have said, as long as they are in an enclosed space and have appropriate safety systems in place, it is probably not a bad idea. As with any types of system, they have to be maintained and operated correctly.
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I'm deliberately _not_ bringing any expertise in the arts and science to the question and ask instead: "I dunno. Is there something to earthquake-proofing structures that makes it more attractive to business concerns than COVID-proofing?" I'd be very surprised if that's not 80% of your answer right there.
It looks like UV technology can be useful in some places but certainly not all. There is no reason to think that it is a "solution" to covid. Retrofitting would not only be expensive but disruptive. Congress is not being generous anymore with billions for any aspect of pandemics. A lot of the world could not afford this technology at all.
What could come closer to a "solution" is a) development of vaccines which could apply to more variants; and b) better and faster distribution of vaccines, especially worldwide. If this is left up mostly to private enterprise - that is if companies see their way to major profits - it would have the advantage of tapping private capital, which is extremely abundant, actually excessive (going into NFT's and crypto instead of productive investment). There are big problems with high prices from the patent system but without a revolution it is how things are going to work for the foreseeable future.
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Not an engineer, but, would UV systems to irradiate recycled air on an aircraft help?
It seems like in an airplane you could just run the air through a glass topped duct running the length of the roof. Plenty of UV at 35,000 feet. Of course it wouldn't work on the ground or for night flights.
Sorry, normal glass doesn’t transmit UV. You would have to use quartz.
or use HEPA filters (which I'm pretty sure they do).
Modern commercial airliners already change the cabin air every two or three minutes. And, as golack mentioned, use HEPA filters.
If you're using it inline in HVAC, you don't need far-UV/far-UV-C; you can just use standard UV-C. Nothing is stopping everyone from using inline UV-C right now. I mentioned this in late spring, 2020.
Stop pointing to the shiny new thing when the old reliable is available and (relatively) affordable.
Here's a link to ch 62 from ASHRAE's handbook re UV-C: https://bityl.co/CODG
Also, this is not the realm of civil engineering. Civil engineering is about site design/construction.
This is mechanical HVAC engineering -- the M in MEP in building design/construction.
Nature link
https://www.nature.com/articles/s41598-022-08462-z
Shows the same room-sized graphic as the post.
Claims 222nm far UV was in safe threshold for 8 hour exposure
Claims 222nm is not a skin or cancer risk, but filtering is needed to remove wavelengths longer than 230nm.
Also, I believe there was a building/architecture ventilation design change after the last flu pandemic - it's the reason why all older buildings are "drafty" and the radiators "over heat": apparently those were very specific decisions that we conveniently forgot going forward as "everyone" knows that vaccines are what's needed to combat the next pandemic. There was a writeup (on Slate? Vox? somewhere) that went over it as we were all looking at "what happened last time?"
Monkeypox is primarily spread by men having sex with men.
If you plan to prevent the spread with UV light you are going to cause some painful sun burns!
You obviously know nothing about monkeypox or UV light.
Ventilation seems a good idea, but the UV stuff sounds like one of these things that would backfire. Killing organisms in the air would probably have some downstream impact and unintended consequences. On the topic of unintended consequences created by fancy new technologies, read the fascinating "under a white sky" by Elizabeth Kolbert. Highly recommended.
Maybe instead of generic paranoia, you should read the refereed literature, cited above. This isn't some fancy new technology.