General information about UV radiation and its generation

Ultraviolet radiation has assumed an important place in our everyday lives – even if this often happens in the background and is not obvious at first glance.

For example, drinking water in many countries tastes strongly of chlorine and smells as pungent as it is unpleasant – but why is this not the case everywhere?

The solution lies, for example, in municipal drinking water disinfection using ultraviolet, which has become widely used. In the private sector as well as in industry and medicine, ultraviolet technology is on the road to success and is used as a recognized, cost-effective and reliable method.

The answers to the “Where / How / Why” can be found on this page.

Physical basics

What is UV radiation?
Ultraviolet radiation is electromagnetic waves with a wavelength of 100 to 380 nm or a frequency of over 789 THz. The energy of a single light quantum is about 3.26 eV. Ultraviolet radiation is not visible.

It belongs to the group of optical wavelengths, which is why the term “UV light” is often used, which is not quite correct. UV radiation can be refracted, reflected, diffracted and absorbed like light of other wavelengths or infrared radiation – however, the reflection behaviour with regard to the choice of material for the reflector cannot be compared with that of the visible range. Ultraviolet radiation can be made indirectly visible by luminescence excitation (see analytical instruments / Wood Light).

What does UV-A, UV-B and UV-C mean and what is the difference?
Ultraviolet radiation was divided into several groups. These groups have different biological effects and technical applications. The following diagram shows in which range of the electromagnetic spectrum UV radiation is found. The entire UV range is defined as 400 – 10 nm. Here, the energy of the light quanta is inversely proportional to the wavelength (the shorter the wavelength, the more energetic the radiation).

 

Range Wavelength Biological effect Technical use
UVA 315-380nm immediate, short tanning; skin aging and wrinkles, practically no erythema (sunburn causing) effect Tanning, photochemical reactions, luminescence, ink curing, lacquer drying, light therapy, forensics, effect light, …
UVB 280-315nm long-term tanning; formation of a protective layer on the skin; penetrates into deeper skin layers, high risk of skin cancer, has a strong erythema effect -> sunburn light therapy / starts tanning, photochemical reactions, luminescence, hardening of printing inks, drying of lacquers, …
UVC 280-100nm very short wavelength, does not reach the earth’s surface, absorption by the uppermost air layers of the earth’s atmosphere Has a very strong decontaminating effect. Very strong erythemal effect physical disinfection technology, photochemical reactions, luminescence, …
VUV (Vakuum UV oder Deep-UV) 200-150nm very short-wave, ozone-forming by dissociation of atmospheric oxygen from O² to O³ (ozone). Only measurable in vacuum. In nitrogen environment (<15 ppm oxygen content) measurable up to 150 nm surface cleaning, photooxidation, surface activation, ozone generation, …

 

Trip into history

Who discovered UV radiation?
As early as 1878 two researchers (A. Downes & T. P. Blunt) discovered the causal relationship between UV radiation and the growth of microorganisms. The aim was to prove that micro-organisms do not multiply without solar radiation. A long time later it was found that short-wave UV radiation in the UV-C range has a decontaminating effect. In the 1960s, with the decoding and research of DNA, this was only fully understood.

Who produced the first UV radiation source?

Richard Küch was the first person to melt quartz glass, the basis for UV radiation sources, in 1890 and founded the “Heraeus Quarzschmelze”. He developed the first quartz lamp in 1904, laying the foundation for the lamp technology that is still used today. The first quartz lamp, whose UV light yield almost corresponded to the spectrum of the sun, was created under the roof of the then “Original Hanau”.

With the development of low-pressure mercury vapour radiation sources, it was possible, for example, to artificially produce UV-C radiation with a disinfection effect. In the course of time, more and more applications for the technically generated UV radiation were discovered and made industrially usable. As a result, new applications are still being found and brought to market maturity year after year.

We accompany you on this way with competence and expertise.

Disinfection - one of the essential UV applications

Why disinfects ultraviolet?
All microorganisms contain, among other things, nucleic acid (the DNA and RNA), which contains the genetic information of the cell. Because the nucleic acids absorb the incident radiation energy, a photochemical process is triggered which damages the reproduction apparatus of microorganisms and inactivates germs. This takes place, among other things, via a frequently occurring “dimer bond” of the thymine building blocks. This happens in a fraction of a second..

 

No resistance against UV possible!

Popularly said: bacteria, viruses, yeast and moulds have no chance against ultraviolet. Because additional resistance cannot be acquired according to scientific knowledge. Most pathogenic germs are even particularly sensitive to UV rays. This is an important advantage of physical disinfection, as it also works, for example, when germs have already acquired resistance to conventional disinfection measures (alcohol, antibiotics, etc.). At this point we would like to point out the MRSA problem, with which many medical facilities have reached the limits of the disinfection and prevention measures practiced so far.

This circumstance of physical disinfection works for all microorganisms, no matter whether it is about frequently occurring E.Coli bacteria, vecal germs, TBC, SARS, anthrax or legionella. However, a sufficient UV dose is essential – and requires appropriate equipment development.

 

No confusion with gamma- and X-rays
As invisible radiation, sunlight also contains ultraviolet and this, like visible light, only works on the surface. Therefore it is also called “soft” radiation. In contrast, there are many short-wave emitters (below 100 nm), such as “hard” X-rays and gamma rays. “Hard” because they can penetrate solid matter and cause severe damage to the human organism. This is impossible with ultraviolet. For this reason there can be no confusion or comparison.

What is the UV dose or irradiation dose?

Every UV radiation source has an electrical power consumption, part of which is emitted in the UV-C range. 90% of the radiation emitted in the UV-C range is generated at 254 nm, the wavelength effective for disinfection. This is called radiation power. The radiant power is therefore the energy emitted per unit time by the radiator.

The irradiance or also called intensity (µW or mW) is the radiated power per unit area (cm²). Decisive for its level is the optimal utilization of the radiator installed in the device as well as the distance to the item to be sterilized.

If the irradiance/intensity is multiplied by time (s), the UV dose/irradiation dose is: UV dose (mWs/cm²) = intensity (mW/cm²) x time (s)

The higher the radiation power and the longer the irradiation time, the greater the disinfecting effect.

What's the lethal dose?

For almost all microorganisms, the “lethal dose” of UV-C radiation is known, from which the cell loses its reproductive property, is inactivated and no self-repair mechanisms can be activated. Due to the cell structure, the lethal dose varies. Pathogenic germs and yeasts are extremely sensitive to UV-C. Some mould spores require a higher UV dose. If necessary, this must be taken into account in the design.

The basis of UV disinfection is the design of the disinfection device or the selection of a suitable radiation source. At the end of the lamp’s service life, a sufficiently high UV dose must be available to ensure an appropriate disinfection performance within the defined irradiation time. The lethal dose varies depending on the micro-organism and cell structure / cell type. Pathogenic germs are very sensitive to UV-C and are inactivated very quickly. Mould spores require a higher UV dose. In practice, e.g. sealing films for yoghurt pots achieve a germ reduction of 99.5 % to 99.9 % within 2 seconds (see Fraunhofer test report for BlueLight modules).

Safety instructions for handling UV radiation

UV radiation is highly effective and requires simple and uncomplicated measures for personal protection. As simple and uncomplicated as these are, it is important to comply with them. We will be happy to explain in detail whether and which measures are necessary for your application or construction.

If you have any questions, please do not hesitate to contact us.

 

 
Description Information
UV radiation UV radiation is dangerous for eyes and skin. UV radiation sources may therefore only be operated under appropriate personal protection measures. This does not apply if the equipment is in closed units from which no UV radiation can escape (water disinfection systems, air disinfection systems based on circulating air, etc.).
Protection against UV UV radiation at 254 nm (UV-C) can be shielded by normal window glass (borosilicate, Duran, etc.), transparent plastics such as Makrolon®, Plexiglas® and practically all opaque materials. In order to reduce the possible disturbing glare effect, the use of coloured material is recommended. Further information on UV filters can be found in the standard “EN 170 – Personal eye protection”. Quartz glass is permeable to UV-C radiation and must not be used as protective glass for personal protection.
Installation / Operation Alternating circuits, information signs or forced shut-offs are to be installed at the responsibility and discretion of the operator. If individual components are put into operation for integration into systems and devices or sample deliveries, the operator is responsible for observing the relevant electrical engineering regulations. Only instructed specialists with appropriate training should commission the components.
Material resistance Objects can become discoloured after long and intensive exposure to UV radiation. We recommend the use of UV-resistant materials. When using ozone-generating radiation sources, please note that ozone has a strong oxidative effect.
Ozone generation When using ozone-generating UV radiation sources, the MAK value (MAK = maximum workplace concentration) of 0.1 ppm must be observed. For experimental setups, it is recommended to use a suitable area with air extraction.
Temperature Low pressure lamps have a fluorescent tube temperature of approx. 40°C during operation, similar to a fluorescent lamp in lighting technology. UV radiation sources with indium amalgam doping become approx. 90°C-100°C hot on the surface of the fluorescent tube (medium pressure sources approx. 850°C-950°C). These radiation sources are to be regarded as potential ignition sources in contact with highly flammable substances. Furthermore, the radiation source must cool down sufficiently before it is touched. To ensure that the radiation source ignites after switching off, radiators doped with indium amalgam should cool down for about 2-5 minutes (medium pressure radiators about 5-15 minutes). Cooling of simple low-pressure lamps is not necessary.

 

Application overview

Area of application        Example applications
UV curing
(of solvent-free paints, varnishes, adhesives and sealing compounds)
  • furniture industry (chairs, tables, kitchen cabinets), door production, ski production
  • Printing industry (especially offset and screen printing, but also all other printing processes):
    z. e.g., magazines, labels, packaging printing
  • Printing of banknotes
  • Production of CD and DVD (protective coating and gluing of the DVD, printing)
  • Electrical industry: e.g. printed circuit board production
  • Circuit board assembly (adhesive curing)
  • Repair of stone chips in car windows (hardening of synthetic resin)
UV disinfection
(of air, water and surfaces)
  • Drinking water: e.g. breweries, beverage producers, drinking water disinfection in households, pensions and hotels, municipal drinking water treatment
  • Process water: cooling water circuits, process water circuits, deep well extraction, algae control of fish ponds
  • Wastewater: Wastewater disinfection in sewage treatment plants
  • Air disinfection: (in hospitals, control measurements to reduce infections caused by airborne transmission of bacterial pathogens within inhabited areas)
  • Sterilisation of packaging materials before filling (e.g. yoghurt pots, sealing films, in the medical industry)
  • Insect traps
  • Product locks in the medical technology and food industry
UV-assisted oxidation
(of organic pollutants in air and water)
  • decomposition of C-H compounds into basic components, then formation of H2O + CO2 + salts with ozone)
  • contaminated groundwater (petrol stations, soil remediation of military areas, ammunition factories, coal refining, gas works)
  • Landfill leachate (with ozone)
  • polluted industrial waste water (metal working and processing industry, dyestuffs of the textile finishing industry, cosmetics industry, pharmaceutical industry, chemical industry, etc.)
  • industry, electrical industry, coal refining, ammunition factories, car wash plants, nuclear power stations, paper/pulp production, leather industry, laundries)
  • Odour elimination
Sun simulation
(for artificial ageing of materials for safety and aesthetic reasons)
  • controlled wood aging (violin and guitar making, furniture industry)
  • Test of windscreens of motor vehicles and aircraft
  • Investigation of the degradation effect of building materials
  • Testing of plastics in the automotive industry and for many other applications
  • oxidative degradation of plant protection products
  • Conversion of various ecologically questionable water and wastewater substances into ecologically safe and biodegradable substances
Preperative photochemistry
  • Production of detergent base materials, artificial fragrances, etc.
  • Vitamin D Synthesis
  • Polymerisations
  • Photobromination
  • Photochlorination
  • Photooxidation
UV analytics  
Ozone production
  • Surface modification of plastics and rubber products (increase of surface tension or condition
  • Waste water and exhaust air treatment
  • Fat reduction in kitchen exhaust systems
  • Odour elimination / deodorization
Medical application / light therapy
  • Treatment of vitamin D3 deficiency symptoms
  • Treatment of psoriasis (psoriasis)
  • Treatment of jaundice in infants
  • Identification of cancer cells in internal organs
  • Cosmetic tanning
Luminescence excitation
  • Authentication of banknotes and stamps
  • Applications in mail sorting machines
  • Effect lighting
  • Quality control (hairline cracks can be made visible with black light, e.g. in aircraft chassis, automatic steering systems)
  • forensic sciences (search for important evidence at the crime scene, search for causes of fire)
  • in auction houses (checking works of art for authenticity)
  • Biotechnology
  • Geology (testing of phosphorescence and fluorescence)