Frequently Asked Questions

1. What is UV light?

UV or Ultraviolet is a form of electromagnetic radiation with a wavelength ranging from 100 nanometres to 400 nanometres(nm). Electromagnetic radiation comes from the sun and is transmitted in waves or particles at different wavelengths and frequencies. This wide range of wavelengths is known as the electromagnetic (EM) spectrum and is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency such as radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays, and gamma-rays.
As you can see Ultraviolet light falls in the range of the EM spectrum between visible light and X-rays.  UV radiation present in sunlight constitutes about 10% of the total electromagnetic radiation output from the Sun.
UV is generally divided into three sub-bands:

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

2. What are the beneficial uses of germicidal UV light?

Germicidal Ultraviolet or UVC  light causes damage to the nucleic acid of microorganisms and deactivates the DNA of bacteria, virus, and other pathogens by forming covalent bonds between certain adjacent bases in the DNA.  It thus destroys their ability to multiply a key factor in the spread of infections.

  • Ultraviolet is a chemical-free and cost-effective approach to disinfection.
  • Germicidal lights eliminate bacteria, mould, fungi, and other germs found in the air that are invisible to the naked eye
  • They sanitise surfaces and eliminate pollutants, disinfecting the air to protect your family from allergies and respiratory infections.

3. How does UVC disinfect?

Unlike other disinfection methods, UV light disinfection offers eco-friendly and effective solutions to inactivate microorganisms in a hassle-free approach. The bacterias, protozoa, and viruses, when exposed to the UV light weaken and are incapacitated to further reproduction and spread of infections.
UVC light has demonstrated efficiency against pathogenic organisms, including the virus responsible for typhoid, cholera, hepatitis, and other viral diseases. The high energy associated with the UV light due to its short wavelength (254 nanometres), when absorbed by the RNA and DNA of the microorganisms damages their nucleic acids and inactivates them.
This absorption of UV energy between adjacent nucleotides results in the formation of new bonds, creating double bonds or dimers. This double bond of adjacent molecules also called dimerisation, particularly thymine, is common photochemical damage. The continuous exposure to UV light forms numerous thymine dimers in the DNA of bacteria and viruses preventing replication and causing an inability to infect.

4. What pathogens can be killed by UVC light?

UVC light is highly effective in inactivating pathogens like bacteria, viruses, and other microorganisms. Due to its high energy, it destroys the molecular bonds that hold together the DNA of viruses and bacteria, including “superbugs,” which have developed a stronger resistance to antibiotics.
There are UV devices available that can produce strong enough UVC light in circulating air or water systems to make them inhospitable environments to microorganisms such as bacteria, viruses, moulds, and other pathogens leaving them unable to perform vital cellular functions.

5. Can UVC kill Coronavirus?

UVC light  has proven to be very effective in inactivation of at least two other coronaviruses that are near relatives of the COVID-19 virus: SARS-CoV-1 and MERS-CoV.  Based on this past research The International Ultraviolet Association (IUVA) has published  its findings on COVID-19 based on the existing research which states that UVC is effective against the Coronavirus as well.
https://www.iuva.org/IUVA-Fact-Sheet-on-UV-Disinfection-for-COVID-19 .
Research conducted by Cornell University has confirmed the effectiveness  of UVC light on COVID-19 coronavirus and published its findings.
However in order to be effective against any pathogen a very high intensity of ultraviolet light is required.   Most UVC LEDs currently available in the market DO NOT give out high levels of radiation needed to inactivate these pathogens there by requiring much longer time to achieve the inactivation.  The actual time needed to kill the different pathogens can be found in the Dosage Chart*.
The best, most effective and proven UVC sources are the low-mercury discharge lamps being used by VIOlight.

6. UVC dosage - Ultraviolet sterilisation dosage for various microorganisms

UV treatment is rapid and, in terms of primary energy use, approximately 20,000 times more efficient than boiling. UV light can have efficient inactivation of bacteria and other microorganisms up to a distance of eight feet on either side and exposure time of 30 minutes is adequate.  But these are general guidelines.  For a more complete and thorough disinfection it’s important to calculate the UVC energy and time needed for inactivation of specific pathogens.  For more details on the exact time needed for deactivation of pathogens please check the Dosage Chart*.
The average bacterium will be killed in 10-20 secs at a distance of six inches from a UV lamp.

7. Is UVC safe for humans?

In human beings, skin exposure to germicidal wavelengths of UV light can cause rapid sunburn and skin cancer. Exposure of the eyes to the UV radiation can produce extremely painful inflammation of the cornea and temporary or permanent vision impairment, up to and including blindness in some cases. UV can also damage the retina of the eye.  EXTREME CAUTION is advised when handling UVC devices and all VIOlight products come with necessary safety and operating instructions.

8. What is the wavelength & frequency of UV?

Ultraviolet light falls in the range of the EM spectrum between visible light and X-rays and has frequencies of about 8 × 1014 to 3 × 1016 cycles per second, or hertz (Hz), and wavelengths of about 380 nanometers (1.5 × 10−5 inches) to about 100 nm (4 × 10−7 inches). UV has a wavelength shorter than visible light and longer than the x-rays. UV wavelength is between 400 nanometres and 100 nanometres.

9. Do I need to wear gloves when replacing UVC lamps?

Yes, before replacing the UV lamp, one must make sure the power source is disconnected or turned OFF.
Do not touch the glass portion of the germicidal UV lamp with bare hands. Use cotton, latex, nitrile or tightly woven fabric gloves before replacing the UVC lamp.

10. How often do I need to replace my UVC lamps?

Even though a UV lamp may produce visible light past the 10,000 hours, the ultraviolet output decreases over time.  You can replace your UV lamp every 9,000 hours or approximately every 12 months. An annual replacement schedule is also recommended for those suffering from allergies and other respiratory conditions.

11. Does UVC damage surrounding materials?

Ultraviolet (UV) radiation consists of photons with high energy relative to visible light, it can cause degradation in the form of physical and chemical changes in susceptible materials.
For example, long-term exposure of germicidal UVC light to plastics will degrade plastics and reduce its useful life.

12. Does UVC damage eyes and skin?

Prolonged, direct exposure to UVC light can cause temporary skin redness and eye irritation. In some cases, exposure of the eyes to the UV radiation can produce extremely painful inflammation of the cornea and temporary or permanent vision impairment, up to and including blindness in some cases. UV can damage the retina of the eye. Exposure to UV rays can cause premature ageing of the skin and signs of sun damage such as wrinkles and leathery skin.

13. Do I have to wear PPE when using UVC?

For disinfection at home, a PPE is not needed. You can either wear either goggles or face shields.  However, it is recommended you wear a PPE during disinfection in hospitals, industries, schools, and offices.

14. Is UVC visible?

Ultraviolet (UV) light has shorter wavelengths than visible light and is invisible to the human eye.

15. Can UVC light disinfect unopened mail?

No, ultraviolet will sanitise only exposed surfaces. The mail will need to be turned over so that both sides of the envelope can be sanitised.

16. Can UVC light be used to disinfect keyboards, phones, keys, and computer mice?

Yes. You can sanitise the exposed solid surfaces of any device using ultraviolet radiation. However, the disinfection does not occur on the internal surfaces of any objects.

17. What are the limitations to the use of UVC light for surface disinfection?

UVC does not penetrate substances like paper, cloth, glass, and certain plastics, only the surfaces exposed to direct uninterrupted path to the UV rays are disinfected.  Shadow areas or hidden areas where the UVC radiation does not fall will not be disinfected.
So the design of the UVC system plays a very important role in ensuring that disinfection is complete & thorough.  It’s important to note microorganisms in water and air are susceptible to UV radiation.

18. How long do the effects of UVC disinfection last?

In general disinfection by UV germicidal lamps last longer than UV-C LEDs. Once disinfected, the area or object disinfected will remain pathogen free till it comes into contact with contaminants again.

19. How often should you disinfect your space with UVC light?

Disinfection at home can happen each time you bring in something new or once every week. In healthcare facilities, industries, schools, and offices disinfection is required every day.

20. What distance and how long do I need to expose an article to UVC light to sanitise it?

Sanitisation is a product of the UVC energy reaching the article being sanitised and the amount of time that the article is exposed to it.  The exact amount of time needed to inactivate microorganisms depends on the intensity of the UV light that falls on the article being sanitised.  The amount of UVC energy received multiplied by the time of exposure is known as dosage.  Different pathogens require different dosages for inactivation.  Please refer our Dosage Chart* for specific dosage recommendations for different pathogens.
In general the closer the article is to the UVC source the more intensity of UVC dodge  it receives.  The more time it’s exposed to the UVC source the more dosage it receives.

21. Important definitions

Disinfection: the process by which most or nearly all microorganisms are killed through use of chemicals, heat, or ultraviolet rays.
Dose: the measure of quantum of UV energy that is delivered to microbes.  It is the product of intensity of the light times the length of exposure. Different types of organisms require a different dose of UV to be inactivated or killed.
Electromagnetic spectrum: The entire spectrum, considered as a continuum, including microwaves, infrared light, ultraviolet light, X-rays, gamma rays, and visible light
Inactivation: To stop the activity of certain biological substances which is critical to stopping its reproductive cycle and ability to spread.
Intensity: The amount of UV energy produced, measured in milliwatts per square centimeter.
Spectrum: A band of radiation produced by separation of the components of light by their different degrees of refraction according to wavelength.  The ultraviolet spectrum of light consists of wavelengths from 100-400 nm.
Pathogen: Any germ or microbe that can cause infections in humans and animals, including viruses, bacteria, and fungi.
Wavelength: The distance between successive crests of a wave, especially points in an electromagnetic wave.  Visible light corresponds to a wavelength range of 400-700 nanometers (nm).
UVA Light: UV spectrum from 320-400 nm. Black lights emit UV-A light.
UVB Light: UV spectrum from 280-320 nm and is most commonly associated with sunburn or freckling, but also produces some germicidal effects.
UVC Light: UV spectrum from 200-280 nm known for its germicidal effects