Far-UVC Light Safely Kills 99.9% of Airborne Coronaviruses

Coronavirus UV Light

A study suggests that using far-UVC light within regulatory limits could reduce airborne virus levels in indoor spaces occupied by people.

More than 99.9% of seasonal coronaviruses present in airborne droplets were killed when exposed to a particular wavelength of ultraviolet light that is safe to use around humans, a new study at Columbia University Irving Medical Center has found.

“Based on our results, continuous airborne disinfection with far-UVC light at the current regulatory limit could greatly reduce the level of airborne virus in indoor environments occupied by people,” says the study’s lead author David Brenner, Ph.D., Higgins Professor of Radiation Biophysics at Columbia University Vagelos College of Physicians and Surgeons and director of the Center for Radiological Research at Columbia University Irving Medical Center.

The research was published on June 24, 2020, in Scientific Reports.


Conventional germicidal UVC light (254 nm wavelength) can be used to disinfect unoccupied spaces such as empty hospital rooms or empty subway cars, but direct exposure to these conventional UV lamps is not possible in occupied public spaces, as this could be a health hazard.

To continuously and safely disinfect occupied indoor areas, researchers at Columbia University Irving Medical Center have been investigating far-UVC light (222 nm wavelength). Far-UVC light cannot penetrate the tear layer of the eye or the outer dead-cell layer of skin so it cannot reach or damage living cells in the body.

The researchers had previously shown that far-UVC light can safely kill airborne influenza viruses.

The new paper extends their research to seasonal coronaviruses, which are structurally similar to the SARS-CoV-2 virus that causes COVID-19.

Study details

In the study, the researchers used a misting device to aerosolize two common coronaviruses. The aerosols containing coronavirus were then flowed through the air in front of a far-UVC lamp. After exposure to far-UVC light, the researchers tested to see how many of the viruses were still alive.

The researchers found that more than 99.9% of the exposed virus had been killed by a very low exposure to far-UVC light.

Based on their results, the researchers estimate that continuous exposure to far-UVC light at the current regulatory limit would kill 90% of airborne viruses in about 8 minutes, 95% in about 11 minutes, 99% in about 16 minutes, and 99.9% in about 25 minutes.

Using far-UVC light in occupied indoor spaces

The sensitivity of the coronaviruses to far-UVC light suggests that it may be feasible and safe to use overhead far-UVC lamps in occupied indoor public places to markedly reduce the risk of person-to-person transmission of coronaviruses, as well as other viruses such as influenza.

Ongoing studies in SARS-CoV-2

In a separate ongoing study, the researchers are testing the efficacy of far-UVC light against airborne SARS-CoV-2. Preliminary data suggest that far-UVC light is just as effective at killing SARS-CoV-2.

“Far-UVC light doesn’t really discriminate between coronavirus types, so we expected that it would kill SARS-CoV-2 in just the same way,” Brenner says. “Since SARS-CoV-2 is largely spread via droplets and aerosols that are coughed and sneezed into the air it’s important to have a tool that can safely inactivate the virus while it’s in the air, particularly while people are around.”

Brenner continues, “Because it’s safe to use in occupied spaces like hospitals, buses, planes, trains, train stations, schools, restaurants, offices, theaters, gyms, and anywhere that people gather indoors, far-UVC light could be used in combination with other measures, like wearing face masks and washing hands, to limit the transmission of SARS-CoV-2 and other viruses.”

Reference: “Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses’ by Manuela Buonanno, David Welch, Igor Shuryak and David J. Brenner, 24 June 2020, Scientific Reports.
DOI: 10.1038/s41598-020-67211-2

9 Comments on "Far-UVC Light Safely Kills 99.9% of Airborne Coronaviruses"

  1. VERONICA ROACH | June 27, 2020 at 10:13 am | Reply

    Well I assume many other people besides me have recently bought ultra-v machines – mine is used in a small bathroom only when no-one is in there – I will be looking for a new machine or 2 or 3 as soon as somebody produces them with this lower SAFE wavelength – lots of potential orders waiting for you !!!

  2. At least one study showed skin damage in humans after using a far-UVC device from one of the few companies making far-UVC equipment. Low doses of far-UVC might be low enough not to harm humans, but UV light doesn’t magically become harmless.

    Also, national and international exposure limits for various wavelenghths of ultraviolet light have existed for decades. 222nm damages human skin and eyes at about 10-30% the rate of “traditional” 254nm UVC, but it’s not harmless.

    It’s also interesting that manufacturers of far-UVC equipment and excimer lamps don’t recommend their products are used in occupied spaces without protection. They don’t want to take on the liability if Columbia’s research is relied upon when far-UVC does cause skin damage.

    Finally, far-UVC is 10-100 times more expensive than regular UVC mercury bulbs. And if both are effective at deactivating viruses and killing pathogens, and neither can be used in occupied spaces without protection — most consumers and businesses would still be better served with traditional ultraviolet technology.

    • Jeffrey Wexler | June 29, 2020 at 4:53 am | Reply

      Really curious about which study DID show skin damage. there is not much literature out there that proves or disproves skin damage at the 222 nm wave length and was allways questioning the efficacy compared to the safety. Unless it is 100% safe to humans if they were to be treated directly with it to destroy pathogens on the surface then as you stated it can only be used in isolated areas where people cannot be. If that is the case using more powerful UV bulbs that are not in this very narrow range which are far less expensive would be the way to go for general pathogen sanitization. Would love to heard and understand more about Far UV-C. I am aware of 2 NASA scientist who have done work on this and so far they say it’s safe. Need proof, not just their word. Other studies needed ASAP.

  3. I’m not scientist, so just some considerations… tests conducted in an empty room would have significantly different results from a room with people in it. It’s been shown that covid-19 particles move throughout the air for up to 3 hours before settling.

    Particles in the air behind objects, etc. where the UVC light doesn’t reach, would still have the active virus for up to 3 hours, so it would effectively mean you would need to use the UVC light for 30 minutes AND wait another 2.5 hours for the particles to settle onto another surface.

    An alternative that effectively neutralizes the virus, even behind, under, above and beside objects where light doesn’t reach, is VUV (Vacuum UV), which produces ozone. Wherever air reaches, so too would ozone (O3). It requires the same amount of time to effectively neutralize the virus – about 30 minutes. And since UVC would require a full 3 hours (for particles to fall), why not use Ozone for 30 minutes then vent for 5 minutes? Save nearly 2.5 hours and neutralize the virus ABOVE – BELOW – BESIDE and BEHIND objects – where UVC cannot reach.

    O3 (ozone) can be vented and it will return to oxygen, or can be converted to oxygen using UV light.

  4. Got a 25w UVC bulb a while back for sterilizing workspace. Within a second of switching on ozone production is immediately apparent. I exposed an arm (while sparing my eyes) for ~20 seconds out of curiosity; result was a pretty damn red-pink sunburn for a few days. Gnarly.

  5. Regarding the above comments: The study on far uvc showing skin damage was with an unfiltered device that also produced some uv at longer wavelengths. When a filter is applied no damage is seen nor is significant ozone produced. Viruses do not need to settle on a surface to be zapped. They are deactivated in the air when exposed to far uvc. Far uvc is not conventional uvc that of course will produce a sunburn at high levels. Far uvc at such levels would produce no burn and yet would inactivate viruses, bacteria, mold spores etc. in a fraction of a second. The current regulatory level for uvc presumes 254nm uvc. When regulation is updated to recognize the safety of 222nm uvc, higher levels will safely zap microbes in seconds. When widely deployed, there will be no more spread of coronaviruses, influenza, tuberculosis, MERSA, mold, mildew, or any disease that depends on airborne or touch means of transmission.

  6. The article is talking about airborne virii, which is great. However, could not an asymptomatic person be shedding virii through conversation, or a casual cough, which, because of the shadows of standing humans, or high standing furniture, partitions, or lab equipment, the shed viruses could live long enough to be breathed in by an uninfected person? It would be difficult to guarantee that the virus would have no shadows to stay alive in. Persons sharing crowded environments would have to be tested, with a test that would take very little time to process. Terry’s idea sounds more efficient, but what is the damage to people from high quantities of Ozone?

  7. I agree with Ken and wanted to mention that the quandary is there is no one single potential solution. A combination of several have their benefits and negative aspects. Sterilizing, sanitizing areas has it advantages, sterilizing humans on the surface as they walk into that area has advantages and maintaining that sterilization after they have entered has its advantages. The quandary how do you do it all as effectively and efficiently as possible to give the best bang for the $$$$. Whoever has that answer is the closest until there is a REAL sustainable and effective vaccine which we all know is at best a year or 2 or more ahead. Having pharma research experience I know we are fast tracking this but really by end of this year or even next year? Of course my fingers are crossed but even supposedly safe Far UV-C is not the panacea. Thoughts.

  8. I am curious as to the power required to kill the virus? The number of lumens required and the distance where the light becomes ineffective. Finally the speed of the air past the LED.

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