What is ultraviolet (UV) light?

Ultraviolet (UV) light is light with wavelengths making it invisible to the human eye. UV light is usually divided into three categories, UVA, UVB and UVC, according to its wavelength.

  • UVA, or near UV (315–400 nm)
  • UVB, or middle UV (280–315 nm)
  • UVC, or far UV (180–280 nm)

How is UV light used for disinfection?

UV light has been used for decades to disinfect hospital rooms and medical equipment. UVC list is used for disinfecting, and it kills bacteria and viruses by damaging their DNA or RNA.

What’s the difference between conventional UVC light and far-UVC light?

The wavelength of conventional UVC light is around 254 nanometers and kills viruses and bacteria very efficiently. UV lamps are used as water purifiers to deactivate living organisms. However, this light can penetrate and damage human skin and eyes, so it cannot be used in occupied rooms or near people.

Far-UVC light has a shorter wavelength of around 222 nanometers. It also kills viruses and bacteria, but according to evidence obtained so far, it is safe for human exposure and can be used in occupied locations.

How do we know that far-UVC light kills the coronavirus that causes COVID-19?

Several research teams have shown that far-UV light efficiently kills human the SARS-CoV-2 coronavirus that causes COVID-19:

University of Milan:

U.S. researchers:

U.S. and Dutch researchers:

How do we know that far-UVC light is safe?

Far-UVC light cannot penetrate the layer of dead cells on the surface of our skin, nor the tear layer covering the surface of our eyes, so it can’t reach any living cells in the human body.

Several research groups have carried out extensive safety studies with far-UVC light and human skin, mouse skin, and mouse eyes, and all evidence suggests that far-UVC light has no harmful effects.

Columbia studies on far-UVC safety in human and mouse skin:

Japanese studies on far-UVC safety in mice:

UK study on far-UVC safety in human skin:

Can far-UVC light prevent the spread of other viruses?

Yes. Far-UVC light is expected to be effective in reducing the spread of all viruses including influenza, measles, the next potential pandemic virus, as well as bacteria and spores.

Will far-UVC light eliminate the need for social distancing, face masks, hand-washing, or vaccines?

These strategies reduce the spread of COVID-19, but none are completely effective on their own. Far-UVC light together with the existing techniques has the potential to limit the spread of the coronavirus and other infectious diseases.

How and where can far-UVC light be used?

Overheard far-UVC lights that continuously kill airborne pathogens can be used in crowded indoor spaces including hospitals, buses, planes, trains, train stations, schools, restaurants, offices, theatres, gyms, etc.

Are 222 nm UV lights in commercial use?

Yes, many places or organizations – ranging from the U.S. Air Force to the Space Needle in Seattle to Boeing – are already using or investigating ways to use UV light in the 222 nm range to protect public health.

What are the regulations concerning the safe use of far-UVC light?

Far-UVC lamps are required to conform with existing safety regulations. In the U.S., the regulations were established by the American Conference of Governmental Industrial Hygienists and the International Commission on Non-Ionizing Radiation Protection.

As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200–222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure.