UVGI fact and figures
Find out how UVGI works and how effective it is
Ultraviolet germicidal irradiation (UVGI) is an effective method for reducing and controlling the spread of many pathogens, including airborne bacteria, viruses, mould spores and other micro-organisms. It inactivates surface and airborne micro-organisms that trigger allergy and asthma symptoms, significantly reduces the spread of infectious diseases caused by bacteria, and reduces or eliminates the need for expensive cleaning services.
This page helps you understand how UVGI works, and gives detailed figures about its effectiveness:
How UV-C works
Ultraviolet light is invisible to the naked eye, and has several varieties. UV-C is the kind that we use in our products. Germicidal UV has a specific wavelength of 253.7 nanometers.
UV-C lamps
Ultraviolet germicidal lamps provide a much more powerful and concentrated source of ultraviolet energy than can be found naturally. Such lamps sanitize air that is passed directly in their path, and surfaces that their light falls on, to destroy pathogens that come into contact with the UV rays.
Modern compact UV-C lamps (ours are made by Philips) are designed to be efficient and reliable generators of exactly the right wavelength of ultraviolet germicidal irradiation (UVGI) to disinfect gases, liquids and solid surfaces. They have a glass envelope to filter out harmful ozone-forming radiation (UV-V). To protect people, they must be used in closed containers, or with some other kind of protection (for example, louvred shielding or mounted high in a room away from the inhabitants).
illuminated UV lamps
Germicidal action
UV-C disrupts the DNA and RNA of micro-organisms including bacteria, viruses and fungi, making it impossible for them to reproduce, and killing a large number in the process. Whilst this action cannot be called sterilisation because some deactivated cells are still present in the environment, the percentage of viable organisms is vastly reduced. Air disinfection units constantly 'chip away' at the population or airborne organisms, keeping levels low. The more aggressive action of the surface decontamination units and cabinets removes up to 99.9% of contaminants when used correctly.
The ultraviolet spectrum
We're all familiar with the visible spectrum, seen in a rainbow or a prism, but sunlight also contains infrared (heat) and ultraviolet light as well, both of which are invisible to humans. Ultraviolet light comes in several different kinds, based on the wavelength:
- UV-A is long wave UV - a significant component of sunlight that's responsible for tanning and immediate sunburn. It's used for insect-killing lights - insects can see some ultraviolet and are attracted to it.
- UV-B is a smaller component of sunlight responsible for deeper sunburn, and most of which is absorbed by the ozone layer.
Exposure to both UV-A and B can result in many health problems, including cataracts, skin aging, skin cancers and immune system depression for instance. However, limited UV is essential for health as it makes Vitamin D, and is used to treat certain skin disorders like psoriasis.
- UV-C, or short wave UV, is the wavelength in which we we are interested. It does not reach the earth's surface in any significant amount, as it is absorbed by the atmosphere, so we have to create it artificially. It can cause burns and eye damage on prolonged exposure if not carefully managed, but has positive uses for air, surface and water disinfection.
- UV-V is generated by certain kinds of ultraviolet lamps that produce ozone (ours do not!). This occurs because UV-V light reacts with oxygen to break it into atomic oxygen, a highly unstable atom that combines with regular oxygen atoms to form ozone. Ozone is good for the upper atmosphere but very reactive, and bad for you if you breathe it in.
Microorganism susceptibility to UV-C
UV-C is effective against a wide range of bacteria, fungi, spores and viruses when used correctly. The table below shows some indicator species, organised in decreasing order of susceptibility:
| Group | Species |
|---|---|
| Vegetative bacteria | Staphylococcus aureus Streptococcus progenies Escherichia coli Pseudomonas aeruginosa Serratia marcescens |
| Mycobacteria | Mycobacterium tuberculosis Mycobacterium bovis Mycobacterium leprae |
| Bacterial spores | Bacillus anthracis Bacillus cereus Bacillus subtilis |
| Fungal spores | Aspergillus versicolor Penicillium chrysogenum Stachybotrys chartarum |
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