What is UVC Light, and How Does It Kill Germs?


Ultraviolet (UV) light is a form of light, invisible to the human eye, that exists on the electromagnetic spectrum between X-rays and visible light. We are exposed to low levels of UV light from the sun’s rays every day, although much of the UV energy is absorbed by the ozone layer.

Ultraviolet Light

You’ve probably seen the visible light spectrum before; on the spectrum, visible light (violet to red) is from 380 nanometers to 780 nm. As a reference, most household lamps are between 500 and 700 nm.You may also be familiar with UVA and UVB (280nm-400nm), related to suntans and sunburns and used in tanning bed applications.


It is generally agreed upon that 254 nanometer UVC is optimal for germ-killing purposes.

Why does UVC work?

At the foundation of a suntan or sunburn is skin cell damage caused by Ultraviolet-A and -B rays given off by the sun. UV rays are harmful. SPF 30, Earth’s atmosphere, and evolution have allowed us and most organisms to develop a tolerance to moderate levels of UVA and UVB. That’s the big difference.

The sun gives off UVC, too, but it’s not strong enough to penetrate Earth’s atmosphere. So, there’s been no chance for infectious bacteria and viruses to develop a similar immunity. Hospitals use UVC to kill germs because its germicidal characteristics can be unequivocally relied upon.

Who uses UVC?


UVC is commonly used in hospitals, air and water filters, microbiology labs, etc. They rely on high strength UVC for disinfecting because it works. It kills germs quickly and effectively. UVC rays attack DNA and paralyze all cellular functions. Bacteria, viruses, and even antibiotic-resistant superbugs have no tolerance to UVC. UVC=dead, that’s it. The germs are dead and unable to contaminate samples or be “caught” by a patient in a hospital.

UVC bulbs, our geeks insist “lamps”, are long linear cylinders–like the bulbs in a high school computer lab or that scene from that one movie. Effectiveness is a function of UVC strength and exposure time. Lamps are normally positioned at short distances from the “target disinfectee” because it works most effectively in the lamp’s line of sight.


UVC wavelengths are between 200 and 300 nanometers, making them germicidal – meaning they are capable of inactivating microorganisms, such as bacteria, viruses and protozoa. This quality makes UVC energy an effective, environmentally-friendly and chemical-free way to prevent microorganisms from replicating in any environment, but especially in hospitals.



The high energy from short wavelength UVC light is absorbed in the cellular RNA and DNA, damaging nucleic acids and preventing microorganisms from infecting and reproducing. This absorption of UVC energy forms new bonds between nucleotides, creating double bonds or “dimers.” Dimerization of molecules, particularly thymine, is the most common type of damage incurred by UVC light in microorganisms. Formation of thymine dimers in the DNA of bacteria and viruses prevents replication and ability to infect.

UV dimerazation


There are three UV light wavelength categories: UVA, UVB and UVC. UVCcleans produces UVC, the only wavelength known to be germicidal. UVC utilizes short-wavelength ultraviolet radiation (shorter than UVB and UVA, which are NOT germicidal) that is harmful to microorganisms.

Broad Spectrum UV disinfection often claims to be more effective than short wavelength UVC, but ultimately wastes a considerable amount of energy with no documented increase in effectiveness – only short wavelength UVC produces the amount of energy necessary to kill microorganisms.