Ultraviolet rays make up part of the natural sunlight’s spectrum. Around the wavelength range of 253, 7 nm they have a bactericidal effect on bacteria, viruses, yeasts and mildew.
By the innovative technology of UV disinfection there are deriving direct advantages for the operator: The technology of UV-C disinfection has no chemistry, no toxic compound and no formation of resistance. Undesirable micro-organisms get inactivated within seconds, whilst the product characteristics persist. In addition the application of UV disinfection meets the high requirements of the consumer protection and the VDI 6022 as well as the HACCP concepts. Not least the application of UV-C disinfection has a positive effect on the IFS certifications.
For a long time the sun light is attributed the characteristics to contain a spread of infections. In 1878 the English scientists Downes and Blunt discovered, that the multiplying of micro-organisms significantly gets reduced when exposed to sunlight. At that time the course of this process could not be cleared yet.
Later researches showed that this effect starts from the invisible part of the solar radiation below the wavelength range of 320 nm. From the moment of this discovery it was possible to originate an artificial radiation source for the generation of bactericidal radiation. The kind of radiation, which causes an inactivation of bacteria, nowadays is well-known as ultraviolet radiation.
The ultraviolet radiation
Ultraviolet radiation, as well as visible light or radio waves is an electromagnetic radiation and cannot be perceived by a human eye. By definition it contains the spectral range of 100 up to 380 nm and thus directly joins the blue, visible part of the light. The ultraviolet spectrum includes wavelengths up to 380 nm and is subdivided as follows:
|380-315 nm "blacklight"|
|315-280 nm responsible for sunburn|
|280-200 nm disinfection effect|
|200-100 nm ozone formation|
Ultraviolet radiation is present in the sunlight. Because of the absorption in Earth’s atmosphere (particularly in the ozone layer) radiations reach the surface of the earth with a wavelength range beyond 300 nm – particularly UV-A and a lower part of UV-B.
UV-C rays are selected from the ozone layer and offer a high disinfection effect.
The UV-C light with 100 to 280 nanometres is the shortest wavelength range of the ultraviolet light. With intact ozone layer however this range of ultraviolet light gets filtered from the solar ray spectrum before impinging upon earth’s surface.
As contrasted to UV-B radiation, which particularly deeply penetrates the epidermis, a causal relation of dermal cancer owing to intensive UV-C radiation could not yet be scientifically proven.
The principle of operation
The extreme high-energy UV-C radiation prompts a photochemical reaction. The wavelengths with 253, 7 nm get absorbed by the cell nucleic acids and, depending on the radiation dosage, lead to a killing, resp. impairment of germs and fungal spores. Hence the UV-C radiation sees use in the targeted impairment or killing of micro-organisms (like e.g. germs, viruses, yeasts and mildew).
The dose principle
The dose principle refers to the fundamental influence of the factors time and performance. The product of irradiation time and irradiation intensity is quoted in mW*s/cm² angegeben.
UV-C dose (mWs/cm²) = intensity (mW/cm²) x time (s)
While simply structured micro-organisms show a high sensitivity to UV-C radiation, i.e. they easily may be deactivated with a minor dose, significantly higher energies are necessary in order to kill mildew and spores. The efficiency of UV-C with the inactivation of micro-organisms therefore always is in direct relation to the applied dose.
That way sterilisation rates of up to 99, 99 % may be economically realised, depending on the requirement. The exact UV-C dose that results in an inactivation of the micro-organisms, type-specifically differs. Whilst the majority of germs and viruses can be inactivated with relatively low doses, yeast, mildew and spores require a multiplicatively higher dose.