What is UV-C Disinfection?

So, you want to know about UV-C disinfection? Well, you’ve come to the right place.

UV-C is an abbreviation for ultraviolet light, subtype C.

Ultraviolet light is part of the electromagnetic spectrum, which includes (in ascending order of wavelength) gamma radiation, X-rays, ultraviolet, visible light, infrared, microwave, and radio waves. The shorter the wavelength of the radiation, the higher the energy. This puts Gamma radiation as the type of electromagnetic radiation with the highest energy, and radio waves as the lowest energy.

Ultraviolet light has a shorter wavelength (Read: more energy) than visible light, but less than X-rays or Gamma rays. Ultraviolet light is typically categorised as having a wavelength between 100nm and 400nm. This is then broken down into further subtypes which have slightly different properties.

For the purposes of this article, we are only going to look at UV-A (315nm-400nm), UV-B (280nm-315nm) and UV-C (200nm-280nm).

One of the biggest differences between UV-A, UV-B and UV-C is their ability to penetrate through physical objects (solids, liquids, and gases). UV-C has the shortest wavelength, so it has more energy that UV-B or UV-A, but cannot penetrate through physical objects as well.

Because of this, our planets ozone layer is very effective at blocking UV-C emitted by our sun (which as you’ll find out later – is very good news for us), but some UV-A and UV-B is still able to get through. Because UV-A is much better at getting through the ozone layer, around 95% of UV light in sunlight is UV-A.

It’s the UV-A and UV-B radiation from the sun that causes sunburn and skin aging.

The germicidal (microorganism killing) properties of UV-C were first discovered in 1877, and in 1903 the Nobel Prize for Medicine was awarded to Niels Finsen for his use of UV against tuberculosis of the skin. In 1910 UV light was used for the first time to disinfect drinking water (in Marseille, France), and by 2001 there were over 6,000 UV water treatment plants in Europe.

The reason why UV-C is so effective at killing microorganisms is that wavelengths between 200nm-300nm are strongly absorbed by nucleic acids. Nucleic acids are also known as DNA and RNA, which carry the genetic instructions for how cells should behave, grow, and reproduce. When DNA or RNA absorbs UV-C light, it sets off a photochemical reaction that causes mutations/damage in the structure of the DNA or RNA. If this damage is sufficient, this will cause either cell death or inactivation of the organism (it will no longer be able to reproduce).

UV-C also has the same effect on the cells of larger organisms, and as such can cause the same kind of damage to skin and eyes that UV-A and UV-B cause from excessive sun exposure, but UV-C will do so much faster. For this reason, UV disinfection systems should be designed to minimise the risk of human exposure.

It has been found that the most effective wavelength of UV-C light for germicidal applications is 265nm, which is very close to the peak wavelength produced by typical low pressure mercury UV-C lamps (254nm).

As such, most (but not all) UV disinfection systems in use today use lamps producing 254nm UV-C light, which can then be directed onto surfaces, into liquids and into the air to kill microorganisms that it comes into contact with.

Providing these systems are designed and built using good engineering practices, they can generally be extremely safe to use in a wide variety of applications.

I hope now you have a basic understanding of what UV-C is and how it works as a germicidal tool, if you’d like to learn more about the technology then please follow or connect with me on LinkedIn as I plan to write more articles on this subject in the near future.

Likewise, if you have a project you’d like to discuss then I can be contacted on LinkedIn, via email ([email protected]) and by phone (07720 076692).

Michael Elrington

JenAct Sales Manager