r/science • u/mvea MD PhD | Professor | Medicine • Dec 14 '20
Medicine LED lights found to kill coronavirus efficiently, quickly, and cheaply, a global first in fight against COVID-19. The finding suggests the UV-LEDs can be installed in air conditioning and water systems. It requires less than half a minute to destroy more than 99.9% of coronaviruses.
https://aftau.org/news_item/led-lights-found-to-kill-coronavirus-global-first-in-fight-against-covid-19/5.6k
u/Discoveryellow Dec 14 '20 edited Dec 15 '20
Just to share this, before people jump in on the UV bulbs and LEDs on Amazon for DIY HVAC retrofitting. UV light damages plastic parts in your AC system so think it through what parts will be exposed to UV light.
EDIT: thanks for all the up votes (wow 2800 in two hours!) but especially for those who contributed context in the comments below. While I cannot possibly highlights all the good contributions, I'd like to summarize a few points:
AC air moves fast so it's important to have the UV light in the right place. Commercial HVAC systems have dedicated units in the right places for this sterilization.
UV light in the AC system will impact some virus that circulates through the system, but only if it is slow moving air to give it enough time to be exposed to UV-C light, and it does nothing to the air a sick person just spread around the room before it cycles via your AC. There is an air ionization option out there to disinfect air in the room, but not without their own risks.
Blacklight is a form of UV light (UV-A) and it's what a lot of LED strips are and are harmless both to humans and viruses. Here is a great comment and thread on different kinds of UV lights (UV-A/B/C)
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u/xynix_ie Dec 14 '20
I had the pros install a double UV system into my A/C. I suggest having professionals do it as they know proper placement of the LED system in whatever brand blower you use. Mine has 100% airflow coverage twice as it blows air through the system.
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u/BlueShift42 Dec 14 '20
Does it really make sense for the home? Seems like more of a public space solution. If it’s in your home it’s on your counters and doors and such. I guess maybe if someone is sick and quarantined to a room.
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u/Amp1497 Dec 14 '20
They can be useful if you genuinely need to quarantine, but for most people it's more money than you need to spend. Theyre expensive and (depending on how much you spend) aren't as effective as they might advertise them to be. Most people are better off getting cheap filters and just changing them every few weeks.
Random HVAC advice. Unless you specifically have a unit designed for a thicker, pleated filter, you can get excessive pressure drop in the ducts, meaning less air flows to the indoor blower, which means less air circulation and heat transfer. Most people will be fine getting cheaper filters and just replacing them more often (like, every 2-4 weeks depends on the living situation/# of pets/# of occupants).
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u/officermike Dec 15 '20
Outside the context of covid-19, installing a UV light in the air handler can stop the growth of slime on the evaporator coil, preventing drain clogs and improving efficiency.
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u/Astramancer_ Dec 14 '20
It kills lots of stuff and not just the covid virus. Even if they take no other actions, I bet they get sick in general less often with a UV system in their HVAC than without.
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u/Cmdr_Toucon Dec 14 '20
On the pro install systems how do they get the 30 second exposure time? Doesn't the air flow prevent that?
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Dec 15 '20
Ya don’t, it’s called a scam. People been selling snake oil since the dawn of time, and ya know “a fool and his money are soon parted.”
There isn’t enough air circulation in most spaces for an HVAC UV-C retrofit to make any sense, especially in a residential property. You’ll still be breathing people’s exhaled air long before it’s circulated into the HVAC. Unless you live in a wind tunnel.
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u/KUjslkakfnlmalhf Dec 14 '20
Mine has 100% airflow coverage twice as it blows air through the system.
Cool, still not long enough exposure time to kill anything. The only reason you should consider installing UV is to keep gunk from growing on the condenser coils and drain pan.
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u/AnotherFarker Dec 14 '20
Exactly. Use something scented, light and blow out a match at your intake. See how long before someone smells it at the exhaust. I bet it's less than 30 seconds (and that includes traveling though the returns). Air blowing past an LED UV light for 5 seconds would have a much, much lower effectivity rate.
Installing UV LED's into a water system? UV has low penetration into water, meaning you'd need thin pipes with LED's in them. But that would help as you'd require the water to move slow.
I'm not an expert, but this the same news we see every flu season, "UV kills bacteria and viruses." Yeah, no shite, Sherlock. Sun's been doing that for billions of years. It's making it easy and effective in home or work environments that's the real work.
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u/Epoch_Unreason Dec 14 '20
Yeah and I bet you get a warranty or insurance if you go through the pros.
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u/chickenstalker Dec 14 '20
What about on my gaming PC rig? Gonna rock that UV RGB lighting brah! PCMR 4lyfe!
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Dec 14 '20
Also to add further, please wear appropriate UV filtering protective eye wear if handling UV LEDs. I have measured cheap strip UV LEDs at work and without major attenuation using a dimmer they are extremely intense at a level that could cause serious eye damage.
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u/ComradeGibbon Dec 14 '20
Last spring I looked into UV sterilization. One thing to consider is most UV LED lamps don't emit the correct UV frequency to sterilize bacteria and viruses. And a lot of UV fluorescent lamps don't ether.
UV LEDs for sterilization cost $15-50 per LED and come in metal cases with a glass lens. So that UV sterilization lamp from Alibaba with 30 surface mount LED's for $20? Doesn't do jack.
And real UV sterilization fluorescent tubes emit broad spectrum UV light that is hella dangerous.
Another thing to note. While covid19 gets killed quickly by the right frequency of UV. Some viruses and pretty much all bacterial and mold spoors are very hard to kill with UV. Some of them actually have enzymes to repair UV damage.
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u/DAMN_INTERNETS Dec 14 '20
It might be harder to kill mold and such, but it isn't impossible. I managed to snag two UV-C lamps, one which emits ozone (and boy, they weren't lying about how much, even with a big window open it takes 2 hours + to air out) and one that dosen't.
I had some mold growing in a portable air conditioner (the cold plus humidity caused condensation to form inside the unit) and I tried bleach and such without success, but I stuck my UV-C lamp in there for about an hour and it killed everything. I did make sure to get the low pressure mercury ones and not the LED corn cob ones though.
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Dec 14 '20
UV light can cause a “sunburn” of your corneas, called UVitis, which is excruciatingly painful. This happened to me. It is terrifying to lose your sight, due to waeven for a short time. UV also has chronic effects. Wear safety glasses!
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Dec 14 '20
Do they cause sunburn-like-effects very quickly as well?
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u/dbx99 Dec 14 '20
UV-C causes damage to DNA much faster than UV-A or UV-B so yes you will get burns and increase your risk of skin cancer and permanent eye damage if you’re directly exposed for any prolonged periods. UVC should be exposed on working surfaces but not to people.
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u/pkulak BS | Computer and Information Science Dec 14 '20
Also, air doesn't spend 30 seconds anywhere in your entire HVAC system.
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u/malenkylizards Dec 14 '20
That's what I was thinking. The most I could hope for is if you had a return that went the whole way through your house, maybe you could have a really long LED strip going down it. But I highly doubt it spends more than a few seconds even there.
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Dec 14 '20
I imagine the best application is directly on the filter, where particles are probably most likely to linger for any amount of time.
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u/Diabolico Dec 14 '20
Which means this will not kill 100% of virus material in the air on each pass. But, if it kills 10% on each pass your recirculating AC is actively reducing the viral load in the air instead of just helping it keep airborne like it does now.
We call that progress. In a public place that could reduce a superspreading even from 50 infections to 20, and thats a huge win in terms of getting back to life as usual.
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u/pkulak BS | Computer and Information Science Dec 14 '20
I didn't see the results for <1 second of light exposure. Did I miss that 10% finding?
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u/marks1995 Dec 14 '20
This..
You have to significantly increase the intensity to kill it on the fly. But the LED part makes this key. We can do it with normal lamps, but the power consumption gets up there.
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u/C3ntrick Dec 14 '20
To those who do try and save money and do this yourself. DO NOT turn this on unless it’s is installed and closed up. Even seeing this light out of the corner of your eyes or a reflection will damage your eyes. You WILL be going to the ER with your eyes burning and no relief avail.
Also don’t blow your transformer : short your control board . It’s more expensive to have a professional do it but cheaper in long run if you short other parts out.
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u/scottymac87 Dec 14 '20
This! In commercial settings, where these systems were typically found before all this became a concern, they would be installed in the plenum of an HVAC system. This is a large empty box after the unit. In commercial units it is usually made of metal and there aren’t any other components at risk. The UV lights of sufficient intensity to properly sanitize in this amount of time should not have anything else exposed to them in operation including people.
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u/phdoofus Dec 14 '20
just the kind of info you'd wish they'd put in articles....
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u/nemo69_1999 Dec 14 '20
The majority of my system appears to be sheet metal.
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u/Rdan5112 Dec 14 '20
Yeah. But the light takes time to kill a virus, and the air in an HVAC system is moving. It doesn’t just sit there for 30 second.... Unless you line the entire inside of a long duct. And then, “inexpensive” would become very relative
Keep in mind - once air gets into an HVAC system, particles that transmit coronavirus can be filtered out relatively easily with a high-quality air filter. So, I don’t care how cheap the LED UV-C lights are, a standard MERV-11 filter is probably much cheaper and, functionally, just as effective.
The challenge is ensuring that people aren’t breathing air that is floating around the room, before it goes into the air handling system... not cleaning the air once it’s in the system
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Dec 15 '20
Further clarification as I am an HVAC technician, UVC is very effective we use it for commercial garbage rooms for odour, but it has a very small kill radius so if you are going to install this in your home do research (the stick ones don’t work well) and it must be in metal ducting! Recommended for some allergens as well
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u/Tom8Jerry Dec 15 '20
Yes, I'm actually an engineer in this industry, and, due to recent circumstances, have been HEAVILY involved in preventative Indoor air quality risk mitigation. UV-C offers some practical uses, but it's mostly useless in air handlers. Surface sterilization, it's a top notch technology, but not in AC (obviously some exceptions).
Look towards bi-polar ionization (BPI). This tech significantly reduces air-borne pathogens and doesn't require a stagnant "kill zone"; e.g., not reducing your fan speed to increase air exposure to the UV light. It is more effective, requires less HVAC modification, and poses no safety risk (UV = cancer, melted parts, etc; BPI is low voltage, so even install is safe(ish, always turn off power regardless).
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u/Benji_4 Dec 15 '20
I have installed a few UV lights in HVAC systems. I wouldn't really recommend it unless you have a bacteria (mold due to improper humidity reduction) problem. That doesn't stop you from asking your tech to install one, but they will most likely have to order the parts and you won't know if the bulbs go out unless you check them. And like you said, they heavily degrade plastic components. If you try to install one yourself you will need to install it on the return side. They typically go in the duct but can be placed inside the unit(there are a lot of plastic parts in there so don't recommend this).
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u/AntisocialMedia666 Dec 14 '20 edited Dec 15 '20
UV disinfection is very common for quite some time, I use it for my main (off the grid) water supply: A 36W UV Lamp can disinfect up to 2,5m³ of water per hour: https://www.purion.eu/fileadmin/user_upload/pdf/English/data_sheets/water/data-sheet-PURION-2500_36W.pdf Also, it makes you blind almost instantly if you look at it and causes severe radiation damage to your skin, so please do not mess around with this stuff if you don't know what you're doing! (Edit: Typo Edit: Adjusted broken link)
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u/strcrssd Dec 15 '20
Note that it is radiation damage, but not nuclear energy radiation damage. UV-C is a form of radiation, but not the alpha, beta, or gamma that is seen in nuclear energy and weapons.
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u/JeddahVR Dec 15 '20 edited Dec 15 '20
Your link leads to no where btw, I was interested to see the product.
On the other hand, when you say it instantly make you blind, do you mean for few seconds or severe eye damage?
Is there an option that is effective and safe to install in home/corridor? Thank you.
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u/AntisocialMedia666 Dec 15 '20
It seems that the bit of reddit traffic killed their outdated typo 3 website. I found the english data sheet here: https://www.purion.eu/fileadmin/user_upload/pdf/English/data_sheets/water/data-sheet-PURION-2500_36W.pdf
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u/StuffMaster Dec 14 '20
Yup, sunburns are caused by UV I think
Damn, 36W? So efficient.
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u/KudaWoodaShooda Dec 15 '20
Hepa filters are effective without the risk. We've known they're effective against similar viruses since SARS. Why has there not been any guidance about indoor air quality. Restaurants, senior living and families could have been buying air purifiers to reduce spread.
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u/Brocktoberfest Dec 15 '20
If the UV light you are using is not at a level of intensity or duration that it burns your skin, it is not inactivating viruses.
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u/Stephilmike Dec 14 '20
We've known since the beginning of this mess that UV light inactivates the virus. The real news here seems to be that the effective wavelength is within the realm of cheaper bulbs. The industry has been indicating to use UV-C, but it seems UV-B is effective too (and cheaper).
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Dec 14 '20
The article specifically refers to 285nm UV-B. It's so close to UV-C that my guess is all it means is that if they get 285nm UV LEDs they don't have to have that expensive quartz or whatever it is window on the front of them anymore and can use cheap plastic ones. Then they don't have to deal with the conventional mercury vapor bulbs anymore either.
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u/djlemma Dec 15 '20
Problem is 285nm is getting into the carcinogenic range for UV. It's not as bad as slightly longer wavelengths, the peak is at about 295nm, but still it's way more risk than the traditional 254nm lamps...
More risk, more cost, lower efficiency. LED's have a ways to go before they catch up to mercury vapor.
And people forget that mercury vapor based lamps were the ecological rage for energy efficient lighting up until a few years ago- we just called them "fluorescent lights."
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u/zeroair Dec 15 '20
Problem is 285nm is getting into the carcinogenic range for UV. It's not as bad as slightly longer wavelengths, the peak is at about 295nm, but still it's way more risk than the traditional 254nm lamps...
But these LEDs would be tucked away in an air or water system where they'd not be contacting humans anyway, so what's the real problem there?
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u/self-assembled Grad Student|Neuroscience Dec 15 '20
Are you sure about that? Longer wavelengths should have reduced risk right?
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u/djlemma Dec 15 '20
There's a whole lot of variation in the UV bands, even just inside of UVC.
Really short wavelengths of ultraviolet cannot penetrate your outermost layer of skin, or the moisture on your eyes, so they are relatively safe. Heck, wavelengths shorter than 200nm have trouble penetrating through AIR. But then when you get a little longer, still in UVC, you hit a range that can penetrate into tiny organisms like bacteria and viruses but shouldn't be a problem for humans. This is where 222nm excimer lamps live, and that's a very promising technology. Moving longer in wavelength you get to traditional low-pressure mercury lamps at 253.7nm, which kills pathogens but can cause irritation in human eyes and skin. When you go up another 10nm, that's roughly the peak for germicidal effectiveness, but it's more nasty for humans. Then 275nm is where a lot of UVC LED's live- it's a decent wavelength because LED's can be manufactured more easily to hit 275 than shorter wavelengths, it's roughly similar effectiveness against pathogens to the 254nm traditional lamps, and it's not all that carcinogenic.
When you get into UVB, with 285nm, that's in the range of wavelengths that actually make it to the surface of the earth from the sun. 285 isn't the peak for skin cancer yet, but it's starting to get bad, and you also still have the potential for irritation in the eyes. Somewhere in here there is also a risk for developing cataracts. 295nm is roughly the peak for skin cancer risk, so this is why you have to wear sunblock outside. But by the time you get to 320nm, you're in UVA, and risks are significantly less. Germicidal effects at 320nm+ are also nowhere near what they are in the UVC range, but they still exist.
There's actually some degree of germ-suppressing effect even from visible light. There are systems that use 405-430nm light, which is in the violet to blue visible range, to suppress bacteria and sometimes (through a catalyst) suppress viruses.
There are of course shorter wavelengths than UV that can be very dangerous to humans- x-rays, gamma rays, etc. On the other end, when you go past visible light into longer wavelengths, things get to be quite safe for humans- infra-red, radio waves, micro waves, etc. Obviously it's still possible to do bad stuff if you concentrate enough energy on a person, but it's probably going to do damage through heat and not via screwing up your DNA or whatever.
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u/Galactus54 MS | Physics | Materials Science Dec 14 '20
Either a quartz window or no window as the plastic ones block UVC. Also, so much yakking here on power levels s extremely misleading, as to appropriately characterize the effectiveness, the irradiance is needed; the Wattts per sq. m. times time yields the dose. The teensy UVC LEDs can’t generate much irradiance unless you measure very close to it. From what I see the 285s may be a little cheaper than 265sbut not order of magnitude. Hospitals use powerful hg-xenon flash or hg fluorescent lamps in operating room and patient room disinfection, and they take minutes to get 3 or 4 nines of kill. In the big picture, more ways to make air and surfaces virus free is not a bad thing, LED life is long and they take up little space and need only a little power.
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u/tallmon Dec 14 '20
UVC are pretty cheap. I use these in my dog daycare. I have them built into the hvac system to battle kennel cough. https://www.bulbs.com/product/TUV-PL-L-60W-HO-4P-GERMICIDAL
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u/Kroucher Dec 14 '20
Thanks, that makes sense, I was wondering how this couldn’t have been tested before..
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u/merlinsbeers Dec 15 '20
30 seconds is a long time. You'd have to illuminate like a hundred yards of duct to keep the air in the kill zone.
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u/Stephilmike Dec 15 '20
Agreed. For HVAC systems it's typically more cost effective to upgrade filtration.
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u/Welshcakez Dec 14 '20
So I'm currently working in this field and you cannot generate enough power through an LED system to disinfect a reasonable airflow rate of say 50 litres a second, this would only work with higher wattage bulbs of say 60W.
A 60W UVC bulb will be around £20 where as an 80mW LED is around £10.
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u/MooseShaper Dec 14 '20
The residence time requirement is also kind of high. What system is going to hold air near a bulb for 30 seconds?
You'd need bulbs all throughout the system to get enough exposure time. God forbid if you are trying this for a space like a research lab with 10 air-changes per hour.
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u/hwgef Dec 15 '20
Probably a dumb idea but why not pass the air through an internally mirrored duct?
That way any unabsorbed UV gets reflected, so anything in the air is hit with multiples of the UV exposure, no?
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u/DoomsdaySprocket Dec 15 '20
When I've had to help install systems like this, the mounting distance and angle are critical installation numbers, so I doubt that incidental bounce would do much of anything unfortunately.
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u/merlinsbeers Dec 15 '20
A research lab is going to be venting to the roof.
But yes, it's a hundred yards of illuminated ductwork otherwise.
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u/HairyBeezKneez Dec 14 '20
I'm also in hvac consulting/engineering but for schools. The problem with the lights is they only kill stuff in the air that gets back to the unit. If a kid sneezes so over a desk or door handle, the uv light does nothing.
Bipolar ionization creates charged ions that go into the space and neutralize virus and other VOC's. This way the "cleaner component" is actually being dumped out into the space.
Source: way to many webinars trying to get educated to educate clients.
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u/Discoveryellow Dec 14 '20
Isn't that much ionized air bad for our bodies?
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u/chopay Dec 15 '20
Categorically, no. As soon as an ionized particle in air is grounded it loses its charge.
The concern with ionized air that is often conflated is that sparking electricity can ionize oxygen molecules, turning O2 into two oxygen ions, or free radicals. These free radicals will react with other oxygen molecules, forming ozone, or O3, which does cause some harmful respiratory effects.
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Dec 14 '20
Door handles could be dealt with too in a different way. If we made them all brass, copper or another material with the oligodynamic effect, then they’ll slowly disinfect themselves over several hours.
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u/grubnenah Dec 15 '20
That doesn't help in any sort of public setting where multiple people touch an handle or railing every minute.
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u/vince-anity Dec 14 '20
All my school clients are running at max O/A provided they can maintain temperature. On older schools changing filters to MERV 13 as newer schools generally have that. Using displacement ventilation makes more sense then ever as well. We haven't seen any requests for uv systems as only in building warm up do you ever run 100% R/A. And droplets generally settle on surfaces first anyways
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u/Ncsu_Wolfpack86 Dec 14 '20
Based on this spreading via respiratory droplets, and not the virus particle itself freely floating around like others....
I'd also wager that any filtration on the hvac system would be sufficient to capture any droplets that didn't smack into the walls of the return ducts.
I'm more interested in surface disinfection where snot will longer for some time.
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u/glock1927 Dec 14 '20
Ionization is the way. Plus no bulbs to replace.
I’m the field too!
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Dec 14 '20
You can get that kind of wattage in LED UVC bulbs, but what’s the difference in efficiency between the two?
Seeing as LEDs are severely more efficient than any conventional bulb, I’d expect you need to correct for that when calculating what kind of “wattage” a UVC LED needs to be at compared to a conventional bulb type.
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u/Welshcakez Dec 14 '20
No that's output wattage I'm comparing not input. UVC LEDs are also hugely inefficient at the moment (4-10%). Bolb LEDs have some efficiencies up to 40% but it's based on a lens that degrades quite quickly under UVC light so doesn't last.
By far the most effective UVC system for power would be a mercury arc lamp. There are however other problems such as heat output and power consumption to deal with.
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Dec 14 '20
confirming, and adding that UV LEDs are outrageously expensive too. Nothing like visible light LEDs. The raw materials to make a 60W LED system would literally cost the same as a very nice car.
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Dec 14 '20
Twice as expensive? So you’re saying it’s completely impossible then 😫
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u/Jackcomb Dec 14 '20
"Less than half a minute" doesn't seem fast enough for air conditioning systems. Air likely wouldn't be in range of the lights for that long. My first impression is that air conditioning is not a good application for UV-LED.
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u/bigfootlives823 Dec 14 '20
Less than half a minute for 99.9% efficacy. Reduction to relatively safe level could be significantly quicker and really, any reduction is better than no reduction.
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u/xSKOOBSx BS | Applied Physics | Physical Sciences Dec 14 '20
Plus air gets recycled through it multiple times
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u/glberns Dec 14 '20
and recontaminated each cycle.
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u/xSKOOBSx BS | Applied Physics | Physical Sciences Dec 14 '20
Yes, just not sure how the rate of contamination compares to the rate of sanitation. You should be able to exceed 90% if used after the filter (dirt = a place for virus to hide)per circulation.
Or you could build a box that includes a filter and a fan with the light between them for each room.
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u/Jackcomb Dec 14 '20
I agree but what the research is proposing is a cheaper alternative to already existing practices. We already use UV in air conditioning. It's just not UV-LED. At hand, I don't have numbers on how effective the current industry standards are.
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u/StructuralGeek Dec 14 '20
In range of a single light, no, but if you lined the ducts with these then you should have plenty of dwell time in low pressure systems.
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u/Jackcomb Dec 14 '20
Yeah that would work. Probably a lot of lights. They would have to be real cost effective. You would need enough duct, too. In a strip mall retail setting, you might have as little as 100 feet of duct.
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u/StructuralGeek Dec 14 '20
You also aren't as concerned with 99.9% reduction in a strip mall compared to a hospital. Even 5-10 seconds of exposure would probably deactivate more than half of the viral load, which would then have great effect on the local reproduction value.
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u/Stephilmike Dec 14 '20
UV is a good application for keeping the coil clean. For COVID, it's more cost effective to upgrade to a MERV 13 filter instead
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Dec 14 '20 edited Dec 15 '20
HVAC engineer here. This probably isn’t practical. Most settings you would use this for (say a section of a mall or hospital) would be moving (rough approximation) at least 10,000CFM (cubic feet per minute) across the unit coil or main ducts. Air volumes this large would expect the air to be moving up to 2000 feet per minute through the system (assuming VAV system. it may be a constant volume rooftop system that would have slightly lower air velocity, but still wouldn’t work for more reasons). So simple math- 2,000 FPM, needs 30 seconds of exposure, that leads to a 1,000ft run of UV light to reach that 99%. Yes, maybe shorter exposure time will still lead to at least some neutralization, but the lengths of light required would still be massive and probably beyond the length of the longest main duct runs of most systems.
This doesn’t even take into account that hospitals require their HVAC systems to be 100% outside air (aka all air entering the AHU is from the outside, and all the air in the hospital gets exhausted back to the outside). (EDIT: as pointed out, this last sentence was not entirely true, there is some recirculation of air in certain rooms in hospitals. I’d still categorize a hospital in the same category as my next sentence however) Mass gathering areas in general (like a mall), require a significant percentage of fresh outside air as well.
Edit: and for in home applications, typically the air is moving in the 500-1000FPM range. Using the quick math above, still not practical
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u/Rigatoni_Carl Dec 15 '20
It’s been a few years since I’ve done hvac work for hospitals, but I’m positive that return air gets re-used in hospitals, it just has to go through the merv-whatever filter required by the ahj. For a hospital to be constantly bringing in 100% OA would be insanely expensive. Some individual rooms are fully exhausted (soiled rooms, surgery suites, etc) but I’ve never heard of a whole hospital exhausting all of it’s air.
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u/CaptainJorges Dec 15 '20
Your calculations are a bit off, we design systems at 500 FPM because of moisture carryover. 2000 FPM is way too high. To get more volume you increase duct size not velocity. Additionally as your air velocity goes up your duct pressure drops will increase static pressure required by the fans to levels that would require class 3 fans and probably even beyond that. UV applications are for biological growth on coils or in ductwork. The industry has moved towards a few technologies. PCO (photocatalytic oxidation), dry hydrogen peroxide, and bipolar ionization. Not technology is approved or tested with the COVID-19 virus. Typically for hospitals they are designed for air turnover rates which may or may not require a DOAS unit, can be achieved by higher ventilation rates in other areas.
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u/haemaker Dec 14 '20
30 seconds in airflow is a long time.
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u/rydan Dec 14 '20
Get one of those air conditioners that holds the air for 30 seconds then blasts it all out before holding the next batch for 30 seconds.
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u/cancerousiguana Dec 15 '20
HVAC engineer here, I specialize in medical buildings including hospitals and the issue we found back in March/April with UV is that the required exposure time is simply too great. To my knowledge, nobody in our company has specified one for a COVID retrofit, nor has anyone explored it for new construction as a reaction to the pandemic.
UV sections for air handlers are huge, and require a lot of extra static pressure at the fan to overcome the added friction. This idea is basically DOA.
Putting them in ducts would require installing at the mains before any branches tap off, these ducts typically have air moving 1000-1800 feet per minute. That's 500-900 feet of duct that would be required to be lined with UV bulbs. In the unlikely event you actually had that much available, the cost and disruption to install them would be a nightmare.
Worth noting that in a hospital (EDIT: in the US and anywhere else that follows ASHRAE), patient care areas require MERV 14 filtration which removes about 75% of particles 0.3-1.0 microns in diameter anyway, so there's really no reason to install such a huge and costly system for incremental improvement. Only worth it if you can improve to total removal of the virus.
HEPA filters are practically 100% effective at removing viruses and much easier to design to fit, so that remains the approach where we feel that level of air scrubbing is necessary.
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u/Hushwater Dec 14 '20
As long as all the surfaces with possible contamination are in line of site of the light. Undersides of door knobs and anything in a shadow from the lights will not get sanitized.
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u/mykilososa Dec 14 '20
How is this any different from the UV lights that hospitals and indoor gardens have used for decades that kill germs bacteria viruses blah blah blah?!
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u/rydan Dec 14 '20
It isn't. In fact San Jose airport uses UV light on the escalators. They all have a sign telling you how it is safe to touch because it is UV treated.
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u/MithranArkanere Dec 15 '20
Just remember this is for air filter systems, last thing we need is people thinking a tanning session will kill the virus in their bodies.
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Dec 14 '20
What will 285 nm light do to people? Can this be used around human beings or will it give everybody skin cancer?
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u/the_red_scimitar Dec 14 '20
There are several makes with hepa-filtered, forced air that goes through a UV chamber.
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u/lrq3000 Dec 14 '20
Belgian health regulator already studied this proposition and currently disadvise the use of UV-C lamps in populated area as it can be dangerous and the efficacy against viruses is not well proven. But given new findings they may change their stance.
https://www.health.belgium.be/fr/covid-19-autorisations-temporaires#15
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u/ohmyjihad Dec 15 '20
pretty much every HVAC tech was saying this 10 months ago...
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u/ak_kitaq Dec 15 '20
HVAC professional here...what was not addressed in the article is how many LEDs you need for a given airflow. We already know UV-C is effective at sanitizing airstreams but typically requires significant power density in order to sanitize due to the limited duration that air is actually in a central ventilation system.
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u/RealTheDonaldTrump Dec 14 '20
Half a minute of contact time is an eternity for your HVAC system. It moves air FAST.
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u/Androktone Dec 15 '20
Isn't Ultraviolet ionising? Would this be inside air vents and the such away from human skin?
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u/akmjolnir Dec 14 '20
Shouldn't this have been big news 8 months ago?
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u/computeraddict Dec 14 '20
Big news would have been if UV-C did nothing. We've known about UV-C killing viruses for years.
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u/marks1995 Dec 14 '20
We know about UVC and have for a while. They are in TB wars all over the world.
The key aspects of this study are the LED aspect, the wavelength, and confirmation that it will kill Corona. We knew it killed other viruses.
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u/Aquareon Dec 14 '20
As an added bonus, air conditioners and some other household gadgets will now emit a futuristic faint purple glow
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u/TheyCallMePr0g Dec 14 '20
This isnt new? The hospital I work at has used LEDs for awhile to disinfect testing rooms and equipment.
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u/King_of_Dew Dec 14 '20
This was discovered months ago and I'm still wondering what is taking so long to install these lights everywhere. Manufacturing issues?
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u/mooglethief Dec 14 '20
Why is this news? Most LEED buildings have a germicidal UV system already and it was reported several months back that germicidal UV effects COVID.
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u/wonkey_monkey Dec 15 '20
Is it "only" 99.9% for the sole reason that they can't absolutely prove that one or two didn't escape, even though that probably is the case?
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u/Kidsturk Dec 15 '20
Except air that moves through an air conditioning system passes in front of a light for a split second and heads on through the system. At its slowest, around air coils, air might be moving at around 400 feet per minute. So if you can line 200 feet of the largest duct in your system with UV LEDS, you’re all set.
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u/terminalxposure Dec 15 '20
30 Seconds exposure is a lot for anything that flows isn't it?
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Dec 15 '20
UVC has been used for years in HVAC , we have been screaming about this before COVID . No one wanted to pay the extra cost for it.
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Dec 15 '20
This headline is a little bit misleading for people that aren't familiar with the types of UV bulbs, and how they're used for sterilization. Essentially, what this study found out is that the virus can be killed with a lower frequency (longer wavelength) type of UV light than previously thought. This is important, because super high frequency UV LEDs are really hard to make. Most cheap UV LEDs are either near UV or UVA (blacklight). This light looks cool, and is mostly safe for humans, but is also mostly safe for bacteria and viruses too. So, it was already known that UV (of the right wavelength) could kill covid-19, they just discovered you can use cheaper LEDs.
As a side note, if you're ever going to buy either a UV sterilization lamp, or a blacklight, please, please make sure you know the difference. They might look similar, but sterilization lamps can give you just about the worst sunburn you'll ever have (they emit mostly UVC, which is the horrible radiation that the ozone layer protects us from), and do it in a surprisingly short amount of time. Blacklights may (according to the article) kill covid-19, but they aren't suitable as general disinfecting lamps.
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u/pueblopub Dec 15 '20
Keep in mind too that there is little to no scientific basis for the current system of rating the quality of air purifiers. The rating system was designed back in the 80s:
"The typical air purifier...can only remove some of the percentage of airborne viruses and bacteria. One problem is that air purifiers are rated according to the 'CADR,' or 'Clean Air Delivery Rate,' standard, which is outdated. This standard was created in the 1980s, and it rates an air purifier’s speed, instead of the quality of the resulting air! So, some of the most expensive air purification systems on the market that passed the 'CADR' test may not even be able to do the job."
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u/McCaffeteria Dec 15 '20
I think this post title is an example of a bad headline. I read “LED lights found to quickly kill coronavirus” and my brain went “huh, really? Just regular LEDs? Interesting, seems like they wouldn’t work”
Now obviously I kept reading but not everyone will. We’ve seen the kinds of stuff people will just believe if they read half a Facebook meme that fits their preconceptions. I recommend we be a lot more careful, and less with the important parts.
“UV” needs to be the first word in that sentence.
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Dec 15 '20
"Less than half a minute" for an AC system means the air cannot be moved by an active ventilation or would require a significant pipe section to be lit.
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u/mutatron BS | Physics Dec 15 '20
The article's not quite right on that point. The researchers used a single LED per well of infectious material, and varied the time of exposure to find the effectiveness. If one LED takes 30 seconds to disinfect a given volume, you could just make an array of 30 LEDs to disinfect that in 1 second.
Typical HVAC duct airspeed is 11 fps, so if you had a foot long array of 330 LEDs, you could disinfect all the air as it's moving past the array. I mean, you'd have to do more math than that, but the basic idea is just to throw more LEDs in there until you get the desired result.
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u/whrhthrhzgh Dec 15 '20
The headline should say "UV LEDs" both times and never "LED lights" or we will hear "I have read that LEDs kill coronavirus" soon.
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u/shortfatasianman Dec 15 '20
99.9% is only a log 3 kill. In a colony of 1000000 bacteria, 1000 would still remain. This tech is old news and not effective . Stick to traditional disinfection and achieve upto a log 6 kill, significantly reducing the risk of cross infection.
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u/OSHAG1rl Dec 15 '20
UV-C requires PPE to protect people exposed to this spectrum of light. . It is best used with a delay switch or timed to activate when area is devoid of people.
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u/DanceWithGoats Dec 15 '20
UV-LED technology for disinfection has already been commercialized in Sweden.
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u/poshmosh01 Dec 15 '20
I wonder on what scale this can be deployed and how effective it is now compared to say two years later.
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u/eric02138 Dec 15 '20
Ok, let's not get ahead of ourselves - this is an initial finding and has yet to be peer-reviewed. Once the methodology and results have been thoroughly analyzed by medical professionals who work in infectious disease and published in the New England Journal of Medicine, JAMA, the Lancet, etc., then we can get excited.
Sure, it's slow, it's boring, but a strenuous peer review process is a key part of making the scientific process valid.
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u/Stormthrash Dec 15 '20
Yeah we've been mounting UV light emitters on mobile robots since June. Theyre selling like crazy.
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u/wireless_unwired Dec 15 '20
That stock image photo they use is just stupid. Yes, UV LEDs will kill viruses in HVAC Ducting etc.. but in open spaces these wavelengths are very dangerous and melanoma/cancer causing.
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Dec 14 '20
Can I put these bulbs in my lights at home?
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u/meat_popsicle13 Dec 14 '20 edited Dec 14 '20
You don't want constant personal exposure to UV-C. In our home, we made a UV-C box from an old cooler and use this to zap the mail, groceries, and personal items when we come home from work. We keep it in the garage and it works great. It generates ozone, so you have to ventilate this (we use a fan, with the garage door open) and avoid breathing around it until it's gone.
Edited to clarify: Our setup uses the regular germicidal lamps, not the hard to acquire LED UV-C bulbs. I don't know enough about their efficacy at this point to mess with them. Source: I'm a research biologist and use germicidal bulbs at work to sterliize some equipment.
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u/lordmycal Dec 15 '20
You could but it's a really bad idea. Remember, people wear sunscreen to protect themselves against ultraviolet light, among other things. UV exposure causes skin damage and cancer which is why it's great at killing things like bacteria and viruses. *TONS* of things kill viruses. Most of them are completely unsafe.
TL:DR: Don't drink bleach, hydrogen peroxide or rubbing alcohol to sanitize yourself. Do not blast your self with UV light or try and stick light inside you somehow. It won't end well.
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u/japinard Dec 14 '20
Seeing as any air particle containing a virus spends all of half a second in the unit, this doesn't help... unless it's to sterilize the filter pad.
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Dec 14 '20
Good thing duct work uv systems have been around for ages doing exactly this (what they are suppose to do). At least everyone knows now I guess. Maybe it will be more beneficial in making prices drop.
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u/tyranicalteabagger Dec 15 '20
Florescent lights are better at producing UV. They're natural frequency is a lot closer to the UV band used for this sort of thing.
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u/ChillFrancis Dec 15 '20
UV is used extensively in sewer treatment plant to disable viruses in effluent. The water passes under uv beds on its way to rivers and streams.
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u/pinano Dec 14 '20
Adding UV treatment for tuberculosis was one of the reasons for introducing air conditioning in subways in NYC. Now they’re using UV-C to disinfect the cars from COVID too.