The level of infection caused by microbiological pollution of the air environment of premises is currently quite high.
Most pathogens are transmitted by air or airborne droplets. This is especially acute in places where there is a large crowd of people with poorly organized ventilation, as well as in rooms with air recirculation.
Preventing the spread of diseases is the goal of the air disinfection process.
Types of UV radiation
Ultraviolet radiation (ultraviolet, UV) is electromagnetic radiation that covers the wavelength range from 100 to 400 nm of the optical spectrum of electromagnetic vibrations, that is, between visible and x-ray radiation.
Types of ultraviolet radiation are shown in the table.
|Name||Abbreviation||Wavelength, nm||Amount of energy per photon, eV|
|Near||NUV||400 - 300||3,1 - 4,13|
|Average||MUV||300 - 200||4,13 - 6,2|
|Further||FUV||200 - 122||6,2 - 10,2|
|Extreme||EUV, XUV||121 - 10||10,2 - 124|
|Vacuum||VUV||200 - 10||6,2 - 124|
|Ultraviolet A, long-wave range||UVA||400 - 315||3,10 - 3,94|
|Ultraviolet B, medium wave||UVB||315 - 280||3,94 - 4,43|
|Ultraviolet C, short wave||UVC||280 - 100||4,43 - 12,4|
Currently, the use of ultraviolet radiation is of great importance, since it is one of the main methods of inactivation of viruses, bacteria and fungi.
Inactivation of microorganisms means the loss of their ability to reproduce after sterilization or disinfection.
Ultraviolet radiation with a wavelength range of 205-315 nm has a bactericidal effect, which causes changes in the DNA of microorganisms, which lead to a slowdown in the rate of their reproduction and further extinction.
As a result of scientific research, it was noted that exposure to UV in the UVC spectrum range at a wavelength of 254 nm is most effective for disinfection.
Living microbial cells react differently to ultraviolet radiation depending on the wavelengths.
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Ultraviolet irradiation of the air is performed using ultraviolet lamps, the principle of operation of which is based on passing an electric discharge through a rarefied gas (including mercury vapour) located inside a glass flask, as a result of which the gas glows and emits radiation.
Ultraviolet (bactericidal) lamps are an artificial source of radiation, in the spectrum of which there is radiation with a wavelength of 205-315 nm.
The most widespread, due to the highly efficient conversion of electrical energy into radiation, are low-pressure mercury discharge lamps, in which the process of electric discharge in an argon-mercury mixture transforms into radiation with a wavelength of 253.7 nm. These lamps have a long service life of 5 000 to 8 000 hours.
There are high-pressure mercury lamps known that, with small overall dimensions, feature a large unit power – from 100 to 1000 W, which, in some cases, allow to reduce the number of irradiators in a bactericidal installation. On the other hand, they are not very economical, have a low bactericidal efficiency and with a service life of up to 1000 hours, they are not widely used.
The operation of bactericidal lamps may be accompanied by the release of ozone. The presence of ozone in the air in high concentrations is dangerous to human health, so the premises where the installations are located must be ventilated either by general-exchange supply and exhaust ventilation systems, or through window openings with an air exchange rate of at least 4 times per hour.
A number of major electric lamp companies (Philips, Osram, Radium, Sylvania, etc.) are currently engaged in the development and production of UV lamps for bactericidal installations.
UV lamps are used to sterilize water, air and surfaces.