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Infectious Diseases

Updated 07 July 2020

Far-UVC light can kill 99.9% of airborne coronaviruses in 25 minutes, a study shows

While traditional germicidal ultraviolet light can also kill viruses, it has far more health hazards than far-UVC light.

  • Scientists have found that far-UVC light is just as effective as germicidal ultraviolet light in eliminating coronaviruses
  • This type of UV light isn’t as damaging to human skin and eyes
  • It could prove to be an important measure in combating the spread of SAR-CoV-2 in indoor public spaces


Scientists have highlighted an existing measure that could help curb the spread of the coronavirus that causes Covid-19, using a form of ultraviolet light. 

While germicidal ultraviolet light has proven to kill airborne pathogens like coronaviruses, it’s incredibly hazardous to human skin and eyes and thus can only be used for decontaminating empty spaces. 

READ: UV light won't treat Covid-19 – but it might disinfect medical gear

But research has shown that far-UVC light (a particular wavelength of ultraviolet light – 207 to 222nm) is just as effective at killing airborne coronaviruses, and if calibrated correctly isn’t strong enough to penetrate human cells, making it safe to use in crowded public spaces indoors. 

Published in Scientific Reports by a research team from Columbia University Irving Medical Centre, they found that using filtered excimer lamps set to 222 nanometres effectively inactivated two airborne coronavirus strains that are very similar to the one that causes Covid-19. 

These two strains account for 15–30% of respiratory infections a year. 

Proven to kill normal flu strains

Sticking to current regulatory exposure limits, the lamps inactivated about 90% of the viruses in about 8 minutes, 95% in about 11 minutes, 99% in about 16 minutes and 99.9% in about 25 minutes.

“Given the rapid spread of the disease, including through asymptomatic carriers, it is of clear importance to explore practical mitigation technologies that can inactivate the airborne virus in public locations and thus limit airborne transmission,” write the researchers. 

Because all coronaviruses are similarly sized on a genome-level, the study hypothesises that it would work just as well for airborne SARS-CoV-2. Far-UVC light has previously also been proven to kill normal flu strains. 

This could provide an effective, inexpensive measure for limiting airborne transmission of the coronavirus currently plaguing the world in public places like hospitals, public transport, restaurants, airports and schools.

READ: Can contact lenses block UV light?

Interestingly, while this study is peer-reviewed and published in a respected journal, there have been some reports on social media of Facebook flagging posts about this research as fake news, probably due to previous erroneous claims made by US President Donald Trump.

In May he mistakenly said that human bodies could be hit by ultraviolet light to kill the coronavirus, but experts quickly explained that it would be impossible for ultraviolet rays to reach deep enough within the body to kill coronavirus in the lungs and other organs.

However, germicidal UV-C light has been used by US hospitals to clean their limited equipment in order to extend their use, but it has limitations as the rays need to hit every surface in order to be effective – even inside masks. 

Image credit: Getty Images