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FACTORS DETERMINING THE OVERALL EFFICACY OF THE UVGI DEVICES

Article By MG Cooling Solutions In UVGI - June 18, 2021

Ultraviolet (UV) light is electromagnetic by nature and abundantly produced by the sun. The most common types are UV-A which have the longest wavelength and doesn’t absorb by the ozone layer, UV-B which have a medium wavelength and is mostly absorbed by the ozone layer and finally UV-C which have a short wavelength and is completely absorbed by the ozone. Modern science created UV-C light having germicidal properties and that can penetrate the cell wall of bacteria and viruses causing alterations in their DNA so that they become non-viable and unable to infect a patient 

The UV air purifier uses short-wavelength ultraviolet light (UVC light) at a wavelength of 254nm to kill the airborne pathogen and microorganisms like mould, bacteria, and viruses to reduce indoor air pollutants and this technology is referred to as ULTRAVIOLET GERMICIDAL IRRADIATION (UVGI). Bacteria and viruses are single-celled microorganisms depending on their DNA to live and this is the basic principle behind UVGI technology. By damaging the DNA of bacteria and viruses through UV light can make them harmless. In UVGI lamps artificial UV-C energy is produced that generates UV radiation by ionising low-pressure mercury vapour. Most UV-C lamps are low-pressure mercury lamp that emits UV energy of wavelength 253.7 nm which is an ideal wavelength that causes alteration in the DNA of microorganisms.

UVGI lamps and devices are being widely used all over the world in various configurations and application to disinfect the air, water and surfaces. Several factors affect the overall performance and efficacy of UVGI devices: –

  • Distance between the UVGI lamp and the microorganisms

 It is an extremely important factor several studies have shown that dosage of UV decreases by approx. the square of the distance from the UVGI lamp. According to this formula dosages at a distance of one inch away from the UV lamp is reduced to one fourth at two inches away and so on

  • The intensity of the UVGI LAMPS

The UVGI lamps intensity can differ significantly from one product to another based on the design, sizes ( diameter & length), quality and construction of the lamps

  • Exposure duration of microorganisms to the UVGI lamps

Time & dosage are directly correlated, if considering all other factors are equal then a microorganism exposed for one second will receive double the dosage of a microorganism compared to a microorganism exposed for half a second 

  • Device design 

Design of the UVGI device can affect its performance, total lamp output is a function of device design, number of lamps, the configuration of the lamp on the device, the height of the lamp, and the components used for reflectivity etc

  • Temperature 

The effectiveness of UVGI devices can be affected by both extremely low and high temperatures due to a reduced output of both low-pressure mercury vapour (LPMV) lamps and luminaire control gear. Even microorganisms show reduced sensitivity to UVGI devices at low temperatures

  • Relative humidity 

Studies have shown that high humidity can reduce the effectiveness of UVGI devices due to a variety of factors that includes DNA conformation, self-repair mechanism and protection from the presence of moisture.

  • Ventilation, mixing of air and air movement

Performance of UVGI devices air disinfection depends on air movement rates. Upper room UVGI effectiveness is dependent on maximising air mixing either through natural convection or mechanically aided. The effectiveness of UVGI devices may be reduced if the mechanical ventilation rates in a room are increased together with equivalent room air mixing. It is strongly recommended to include mixing fans with UVGI installation when there is no mechanical ventilation present in the room.

  • Sunlight

Many microorganism exhibit the ability to repair damaged DNA through a process of photo-reactivation. Since the photo-reactivation rate counters the deactivation rate, it reduces the overall effectiveness of UVGI devices. The potential reactivation rate in a room can be decreased by shading the indoor space from direct sunlight

It is very important to consider all the factors so that UVGI devices can be properly installed to delivering their maximum efficiency

MG Cooling Solutions is constantly working to provide a better and safer indoor environment that will improve your health and increase your productivity. Our qualified engineers will examine your space while considering UVGI performance factors so that you will get the maximum benefit of UVGI

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