How Does Germicidal UV-C Light Work?

Concerns over Tuberculosis, bioterrorism, pandemic influenza, severe acute respiratory syndrome (SARS), and now COVID-19 has increased and intensified efforts to utilize UV-C light in air disinfection. 

For decades UV-C light has been underutilized – being designated to only medical facilities, airlines, and some big tech companies. The ultraviolet light that kills germs, bacteria, viruses, and other pathogens is the Ultraviolet C (UV-C) wavelength. The official name of the practice of utilizing UV-C light to sanitize, disinfect, and sterilize air and surfaces is Ultraviolet Germicidal Irradiation (UVGI).


  • Names of germicidal UV light – UVGI light, UV-C light, Germicidal light, UVC radiation
  • History of UVGI – since 1877, UV-C light has been confirmed to kill airborne infection
  • What is UV-C light? – smallest UV light wavelength
  • How UV-C light works to kill pathogens – destroys DNA and prevents vital cell function

About Viral Clean’s UV-C Light Service

We use UV-C light to kill microorganisms in the air and on the surfaces of homes, apartments, businesses, and organizations.

Some UV-C light equipment produces ozone which is harmful and means that people cannot reenter the area that was just sanitized for an undetermined amount of time. Viral Clean Now uses UV-C technology that does not create ozone.

Our service is better than a DIY UV-C wand or lamp because UV-C is a type of radiation, gets absorbed by dead skin and the eyes and easily causes damage to skin and eyes. This is why the CDC says that UV-C is dangerous for in-home use when used by a professional. The CDC does not recommend using UV-C light if you are not a trained professional.

You can find UV-C lights as cheap as $99, but wattage, wavelength, and air circulation are important when disinfecting rooms. Our equipment is $10,000+, tested, and the best on the market. Not to mention we are trained creating the type of air circulation that is absolutely critical to using UV-C light for disinfection. Without proper circulation you’re basically wasting your time. Another thing to know about UV-C wands and lamps is that many sellers offer underpowered or fake UV-C lights.

With a 13 watt light bulb, viruses die when exposed to UV-C light between 6-25 seconds in a 10×16 foot room. Viral Clean Now utilizes 36-48 watt UV-C light bulbs so viruses die quicker and with less exposure. This also means that we can sanitize larger rooms faster.

We not only have hazmat suits that have been cleaned by the light before we enter a home or facility to disinfect, but we also use remote controlled equipment which limits our exposure to the infected area.

History of UVGI

UV light was discovered in 1801, but the power of UV-C wasn’t discovered until the late 1800s.

  • 1877 – discovered the UV-C light prevented microbial growth
  • 1930 – Believed that 265 nanometers is peak effectiveness wavelength
  • 1933 – Discovered that airborne infections are possible via droplets in the air
  • 1935 – UVGI demonstrated to inactivate airborne microorganisms
  • 1940s-1950 – Illusory correlation causes people to abandon UVGI light for air disinfection
  • 1956-1962 – Demonstrated that UVGI kills Tuberculosis (TB) in the air
  • 1969-1972 – Confirm that UVGI is less effective at high humidity
  • 1974-1975 – Confirm that upper-room UVGI reduces TB infection
  • 1985-1992 – A rise in TB renews interest in UVGI for air disinfection
  • 1990s-Present – More studies confirm the effectiveness of UVGI for air sanitization


What is UV-C Light?

UV-C light is the smallest wavelength of the three Ultraviolet light wavelengths.

  • UV-C, from 100 nanometers (nm) to 280 nm – disinfection is usually performed at 254 nm
  • UV-B, from 280 nm to 315 nm
  • UV-A, from 315 nm to 400 nm

UV-C light is a well known air, water, and nonporous surface disinfectant. This is why UV-C is known as the germicidal wavelength.

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How Does UVGI (UV-C) Light Work?

“Ultraviolet germicidal irradiation (UVGI) is an established means of disinfection and can be used to prevent the spread of certain infectious diseases. Low-pressure mercury (Hg) discharge lamps are commonly used in UVGI applications and emit shortwave ultraviolet-C (UV-C, 100–280 nanometer [nm]) radiation, primarily at 254 nm. UV-C radiation kills or inactivates microbes by damaging their deoxyribonucleic acid (DNA). The principal mode of inactivation occurs when the absorption of a photon forms pyrimidine dimers between adjacent thymine bases and renders the microbe incapable of replicating. UVGI can be used to disinfect air, water, and surfaces, although surface disinfection is limited by microshadows and absorptive protective layers.” – National Center for Biotechnology Information

Air disinfection is accomplished via several methods:

  1. Irradiating the upper-room air only
  2. Irradiating the full room (when the room is not occupied or protective clothing is worn)
  3. Irradiating air as it passes through enclosed air-circulation and heating, ventilation, and air-conditioning (HVAC) systems

UVGI is also used in self-contained room air disinfection units.

Essentially, UV-C light is radiation strong enough to destroy the DNA of the microorganism which kills it, inactivates its function rendering it essentially dead, and prevents it from replicating or reproducing (they become sterile). It does this by splitting the bonds that keep DNA intact.

Viral Clean Now uses the second mentioned method of air disinfection – irradiating the full room. The difference is that we do not allow people in the room, even with personal protective equipment (PPE) except for trained Viral Clean Now disinfection specialists.

How The UV-C Lamps Work

Ultraviolet (UV) light is a small range of light on the electromagnetic spectrum emitted from the sun that is between 100-400 nm. There are three categories of UV light – A, B, C. UV-C is the shortest of the wavelengths, and are absorbed by the protecting ozone layer.

Mercury is an advantageous gas for UV disinfection applications because it emits light in the germicidal (‘germs killing’) wavelength range. The light output depends on the concentration of mercury atoms, which is directly related to the mercury vapor pressure.

Mercury at low vapour pressure produces essentially monochromatic (single wavelength) UV light at 254 nm, so-called low-pressure UV lamps.

Exposure to UV light in the wavelength spectrum of 100 – 280 nm damages the genetic (DNA and RNA) and other molecules inside a microorganism. The damage kills the specific microorganism.

Bacteria, protozoa, viruses, fungi, algae are all sensitive to UV-C light.

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