UVC Germicidal effect and inactivation

Is UVC the latest in disinfection? In fact, the effect of UVC light has been known for over 100 years, and was already described in Denmark in 1903, as a method against tuberculosis (Lupis vulgaris), by the Danish Nobel Prize winner Niels Ryberg Finsen.

Germicidal effect and inactivation:

The way traditional UVC works is by penetrating the cells and destroying the hydrogen bonds in DNA and RNA. It has been found that this happens most optimally at a wavelength around 260 nm. However, it may vary slightly, depending on the different pathogens – so it can be beneficial to have a natural light scattering between 240 and 280 nm.

This means that depending on the individual pathogens structure of RNA and DNA, it will require very different amounts of energy to destroy these bonds. Therefore, it is important to know the exact dose needed to destroy the pathogen you want to inactivate. This varies individually, also between the different groups.

There are bacteria that easily can be inactivated with a low dose of e.g., 20 J/m2, but there are also bacteria that require more than 500 J/m2 and the same applies to viruses where the differences can be very large. If we look at yeast and mold, a dose of up to 10,000 J/m2 may be needed.


Deactivation rate:

When working with inactivation of bacteria and viruses, you always look at how large a part of a given colony you can inactivate. This is typically described as the effect you have of your disinfection. It is most often calculated as a percentage as 90%, 99%, 99.9% and up to 99.999%. But common to all is that 100% cannot be done – regardless of whether you use chemistry or UVC light. There will always be a part of a population that survives.

When looking at standard figures for the use of UVC, these are typically calculated at a rate of 90%. The dose which is reported, is the one who will achieve a 90% reduction of a population. Typically, if you want to go from 90 to 99%, it requires twice the amount of energy and the same goes for increasing from 99% to 99.9%. However, you should always examine it specifically for the pathogen you want to reduce, as there also are variations here.

If you come across products that promise 100% or 99.999% effect/inactivation rate of all pathogens, you should have a natural skepticism. This will require an extremely large amount of energy, as mentioned, there are pathogens that require over 10,000 J/m2 to achieve 90% reduction.

At the same time, there is a big difference in how the laboratory tests the effect on a pathogen in a clinical solution of clear water, – in relation to how energy will reach in a specific case in a factory or office.


This is where your supplier’s experience and qualifications come in

We are always happy to come visit for a non-committal talk and for a control measurement of your UVC system.

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