The effect of UVC

When using UVC for disinfection, it is very important that you use the right dose. One must know the exact pathogen, the environment and the surroundings. Here you can get important knowledge on what to consider and what to look after, using UVC.

Terminology

When you have a UVC lamp, it emits light with a given power. This is measured in W/m2 or mW/cm2.

When the lamp is lit on a subject or a pathogen over time (seconds), you get a dose. Dose is effect x time in seconds and is denoted by W x s/m2. It is the same as J/m2. It can also be expressed as mW x s/cm2 which is the same as mJ/cm2.

The power is used to calculate how long a given lamp at a given distance must treat a pathogen to inactivate its DNA/RNA.

 

The effect of UVC

If you search the internet, you will easily find charts like the one below, indicating the dose required to inactivate a given percentage of a particular pathogen:

The chart lists the micro-organism in question and the dose required to achieve a 90% reduction: This is the correct way to indicate the effect, as you afterwards can calculate your lamp type, lamp size and how long it must be lit to achieve the listed effect.

 

Microorganism Dose UV light in J/m2 to achieve 90% reduction Microorganism Dose UV light in J/m2 to achieve 90% reduction
Bacillus anthracis – Anthrax 45,2 Vibrio comma – Cholera 33,75
Clostridium tetani 130,0 Mucor racemosus A 170,0
Corynebacterium diphtheriae 33,7 Penicillium roqueforti 130,0
Ebertelia typhosa 21,4 Chlorella Vulgaris 130,0
Escherichia coli 30,0 Paramecium 110,0
Listeria Monocytes 45,0 Bacteriophage – E. Coli 26,0
MRSA 32,0 Infectious Hepatitis 58,0
Mycobacterium tuberculosis 62,0 Influenza 34,0
Pseudomonas aeruginosa 55,0 Brewers yeast 33,0
Pseudomonas fluorescens 35,0 Common yeast cake 60,0
Salmonella enteritidis 40,0 Saccharomyces spores 80,0

 

What we are missing here, is whether the effect in question has been found in:

  • Air
  • Water
  • On surfaces

There is a big difference in UVC effect in the three situations, and again here it will be the supplier´s experience and material that can be decisive in finding the right dose.

 

General advice

  • Generally, the lowest dose is required in air
  • Generally, medium dose is required in water
  • Generally, the highest dose is required on surfaces

Therefore, it is important to be aware of how a given dose is calculated.

In the case of critical tasks, such as in food productions or pharmaceutical industries, it can be an advantage to test the effect of the UVC unit together with the supplier.

 

We are also happy to come and measure the effect of your system, just as we always offer on-site control measurement of our solutions.

 

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