Ultraviolet light can be harnessed for many beneficial applications such as treating a newborn for jaundice. More specifically, the unique germ-killing properties of UV-C light have been known for over a century.

Since UV-C in sunlight is filtered by the earth’s atmosphere, microbes (including viruses) have no defense against it. This chemical-free technology is now used for hospital disinfection, food safety, and water purification.

What is UV-C?

The UV-C light spectrum includes wavelengths from 200 to 280 nanometers.* The “C” frequency of the electromagnetic UV family has, among other things, germicidal effects. These wavelengths are known for their ability to eliminate 99.9% of pathogens, such as viruses, bacteria, fungi, and mold spores.

Traditional UV-C uses energy from the 254 nm wavelength. UV-C LEDs, which are relatively new, are generally 260 to 280 nm; and far-UVC uses energy from the 222 nm wavelength.

Scientists have found that both UV-C 254 nm and far-UVC 222 nm efficiently and safely kill airborne coronaviruses, including SARS-CoV-2, the virus which causes COVID-19. As a result, businesses are implementing UV-C technology to protect their employees, customers and families.

So what’s the difference between UV-C 254 nm and far-UVC 222 nm?

    Far UVC

    Photo Source: CBS Evening News

    UV-C 254 nm

    Faster disinfection time – can kill coronavirus in zero to two seconds.

    • Dangerous to eyes and skin – can burn the eyes and skin so it has to be used out of sight; i.e., hidden inside the AC system so that it is not close enough to a vent for people to see it through. Caution is required for the installation and maintenance of this technology. 
    • Used for decades – study after study has proven that UV-C light can disinfect air and surfaces. Scientific references abound for UV-C’s efficacy both in literature and in reports of field applications. Of the government reports, NIOSH, OSHA, CDC, GSA, EPA are the most notable. Hospitals and medical buildings have used UV light for decades to reduce transmission and eliminate the hardest bacteria.

    Kills 99.9% of airborne viruses in 0-2 seconds

    Far-UVC 222 nm

    Disinfection time – can kill coronavirus in about 20 minutes.

    Scientists 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 the following percentages of airborne viruses:

    90% in about 8 minutes

    95% in about 11 minutes

    99% in about 16 minutes

    99.9% in about 25 minutes

    • Safe for eyes and skin – since far-UVC uses a lower range of wavelengths (between 207 and 222 nm) for disinfection it can penetrate tiny things the size of a virus. However, it cannot penetrate the depth of human cells, so it does not hurt our eyes or skin. So it’s safe for humans but not for pathogens.
    • Constant disinfection to kill dangerous pathogens – Because far-UVC is safe for skin and eyes, products using far-UVC light can run constantly. They can work at all times to kill pathogens like viruses and bacteria so you are never starting from ground zero.
    • In the last decade – scientists found that far-UVC is also effective at inactivating airborne human coronaviruses. More recently, since the emergence of the novel coronavirus, researchers have discovered that far-UVC is just as effective at killing SARS-CoV-2, the virus that causes COVID-19.

    Using far-UVC light in occupied indoor spaces

    The sensitivity of the coronaviruses to far-UVC light indicates that it is feasible and safe to use overhead far-UVC light in occupied indoor public places to markedly reduce the risk of transmission of airborne pathogens.

    Dr. David Brenner’s (scientist at Columbia University) research on far-UVC was released in a study in June 2020 explaining how far-UVC safely kills coronaviruses. However, he started talking about the benefits of far-UVC several years before the COVID-19 pandemic when he said:

    “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.”


    Photo source: Biospace

    Which Will You Choose?

    Both far-UVC and UV-C prevent the spread of airborne pathogens including SARS-CoV-2 the virus that causes COVID-19. Understanding the differences can help businesses, schools and families make intelligent decisions regarding which applications work best in their environments.

    At White Coat Disinfecting we offer UV-C Disinfection using both UV-C and far-UVC implementations. We install Germicidal UV-C light inside HVAC systems and also have many options for installing far-UVC light fixtures in homes and offices. Our specialists are available to walk you through the process and help you choose the right implementation based on your needs. Please do not hesitate to contact us at 321-795-9800 with questions.

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    *The wavelength of light is expressed in nanometers (abbreviated nm); one nanometer is 1 billionth of a meter.

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