1. UV radiation
UV-C is part of the electromagnetic spectrum that ranges from 100-400nm. Because of the different characteristics of the wavelength regions within the range of the ultraviolet radiation, a subdivision has been made in Vacuum UV (100-200nm), UV-C (200-280nm), UV-B (280-315nm) and UV-A ( 315-400nm). UV-C (254nm) is mainly used for disinfection. The disinfecting effect of UV-C radiation has been known for more than 100 years and is used worldwide in a wide variety of applications.
2. The disinfecting effect
UV-C has a disinfecting effect because it affects the DNA structures of micro-organisms. It causes a photochemical effect in thymines. These dimerise, which means that two adjacent information carriers are improperly linked. This molecular change makes the DNA unusable for the essential process of transcription (metabolism) and replication (cell division). As a result, the micro-organism is made harmless and dies.
3. UV-C lamps
The most efficient method to produce UV-C is in the low-pressure mercury vapor discharge lamp, in which an average of 35% of the energy is converted to UV-C. Lamps of good quality are made of a special form of glass that blocks ozone-forming radiation and have a minimal dose of mercury. Philips lamps are also equipped with a special coating that keeps the intensity of radiation at least at 80% of the initial intensity until the end of its life.
For the exposure to UV-C radiation regulations exist. The Commission of the European Community has created a proposal for a guideline. In this proposal, the Threshold Limit Values for UV radiation as defined by the American Conference of Governmental Industrial Hygienists (1993) was acquired. The TLVs applicable to exposure to UV-C radiation at 254 nm, are based on a value of 0,2 μWcm2 at a continuous exposure for 8 hours. The intensity of the radiation and the time of exposure together determine the dose. This means that variations in the intensity or exposure time interact inversely proportional. Overexposure to UV-C 254nm causes irritation of the skin (erythema) and eyes (conjunctivitis). These consequences can be painful but have no long term effect. The short-wave UV-C radiation, as opposed to UV with a longer wavelength, does not penetrate into the deeper layers of the skin or in the lens of the eye.
Naturally G.L.A. has the knowledge and the equipment to organise an efficient and safe installation. In addition, G.L.A. has more than 25 years of experience in the application of UV-C for air-, surface- and water-disinfection in virtually any industry.
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