Ultra Violet Germicidal Irradiation (UVGI)
Ultraviolet is that part of electromagnetic radiation bounded by the lower wavelength extreme of the visible spectrum and the upper end of the X-ray radiation band. The spectral range of ultraviolet radiation is, by definition between 100 and 400nm (1nm=10-9m) and is invisible to human eyes.
UV spectrum is subdivided into three bands:
- UV-A (long-wave)from 315 to 400 nm
- UV-B (medium-wave)from 280 to 315 nm
- UV-C (short-wave)from 100 to 280 nm
The portion of the UV spectrum (the “germicidal” region) that is important for the disinfection is the range that is absorbed by DNA (RNA in some viruses). This “germicidal range” is approximately 200 – 300 nm, with a peak of germicidal effectiveness at about 265 nm. The absorption of a UV photon by the DNA chain of dangerous microrganisms causes a distruption of a link and consequently an inhibition of DNA replication.
There are different types of lamps:
- 265,0 nm peak of germicidal effect
- 253,7 nm common UV-C bulbs
- 280,0 nm length used by LED (NEW!!)
The discharge lamp is a type of bulb based on the light emission by luminescence from an ionized gas. The ionization of the gas is obtained by means of a potential difference, which migrates the free electrons and positive ions to the different ends of the lamp (where there are electrodes).
- Low pressure UV lamps. These offer high efficiency (approximately 35% UV-C) but low power, typically 1 W/cm (power per unit of arc length). They produce ultraviolet radiation at 254 nm.
- UV amalgam lamps. A high power version of low pressure lamps. They operate at higher temperatures and have a lifetime of up to 16000 hours. Their efficiency is slightly lower than that of traditional low-pressure lamps (approximately 33% UV-C) and the power density is about 2-3 W/cm.
- Medium pressure UV lamps. These lamps have a spectrum with a pronounced peak and high radiation production but a low efficiency of 15% or less of UV-C. Typical power density is 30 W/cm³ or larger. They produce polychromatic light from 200 nm up to visible and infrared light. Depending on the quartz glass used for the lamp body, low pressure and amalgam lamps emit light at 254 nm and 185 nm (by oxidation). Light at 185 nm is used to produce ozone.
All these UV-C sources are exhausted both by the "discharge" of the gas contained within the bulb and by the progressive loss of transparency of the glass that forms them, in which walls are deposited electrons.
these is the tipology
The UV-C lamps can be divided into:
LED New tecnology
- Common UVGI Lamps
- High Output (H.O.)
- Medium Pressure
- LED uv-c
The most innovative source of ultraviolet rays are UV-C LEDs.
These microscopic UV light sources are able to achieve same results as standard UV lamps while offering revolutionary features in terms of portability, power and applicability.
Since their recent implementation it has been possible to design new products for the sanitation of water and surfaces that cannot even be imagined just until a few years ago.
UV-C Light Emitting Diodes (LEDs).
LEDs are optoelectronic devices that exploit the properties of semiconductor materials. They consist of three layers: the so-called n layer, which contains electrons, the p layer, with gaps (i.e. positive charge carriers), and an intermediate layer (the active layer) consisting of the semiconductor. By applying voltage to the n and p layers, electrons combine with the gaps and emit photons - i.e., LIGHT.
Unlike traditional light sources, whose output wavelength is fixed, UV LEDs can be manufactured to operate at the optimum wavelength for the application:
- 265nm is widely recognized as the peak absorption of DNA; however, 275-280 nm is widely used for their great stability.
UV LEDs also switch on and off instantly and can actually be pulsed without any detriment to lifetime, making them more user-friendly and safer for the operator.
The design rules for UV LEDs open new opportunities of what can be disinfected: we are no longer limited to a long tube, but can mount the LEDs in flat panels; on flexible circuit boards; on the outside of cylinders; the options are almost endless
UV-C LED : NO HEAT, WAVELENGTH SELECTION, INSTANT POWER, MERCURY FREE, DESIGN EXTREME FLEXIBILITY
UV-C lamp : LOW POWER, UNCERTAINTY IN TECHNICAL VALUES, PRICE, RELIABILITY, DESIGNED-PER-VOLUME