There are differences in susceptibility to UVC disinfection, but all tested organisms, including various coronaviruses, responded well when exposed to appropriate doses. compiled data from several studies on the UV dose necessary to achieve inactivation of bacteria, protozoa, viruses, and algae, i.e., the loss of their reproductive capacity. Įach different organism has a different sensitivity to UVGI. UVC radiation is strongly absorbed by proteins and nucleic acids, such as DNA and RNA, which makes it an efficient method of abating pathogens, since it generates significant changes in their nucleic acids, leaving them unable to perform important metabolic functions. Used for decades in healthcare facilities, UVGI is known to inactivate microorganisms on surfaces and airborne, limiting their ability to grow and multiply when inhaled or aspirated. The UV radiation emitted by the Sun and reaching the surface of the Earth falls in the spectral UV regions called UVA and UVB, which are less energetic, while the UVC from the Sun is blocked by the ozone layer. The UVC range is 100–280 nm, the most effective wavelength range of UVGI for the inactivation of microorganisms is 250 to 270 nm, and the maximum effectiveness is at 265 nm. While ultraviolet (UV) is the denomination of any radiant energy with a wavelength between 100 and 400 nm, UVGI uses mainly short-wave ultraviolet (UVC) light. Ultraviolet germicidal irradiation (UVGI) radiation has been studied by several researchers and used extensively for over 40 years in the disinfection of water, air, laboratories, pharmaceutical products, and surfaces in general against human pathogens. Furthermore, disinfection and decontamination to mitigate biological threats to people congregating within buildings have assumed great importance due to the recognized increase in threats of bioterrorism, in addition to the pandemic of COVID-19. Multiresistant strains of airborne infectious agents have proliferated worldwide in recent years. In addition, we believe that this study may provide useful evidence and guidance for the design of equipment intended to abate the microorganisms that may be used in CBRNE terror attacks. In this paper, we present our encouraging results, demonstrating the effectiveness of the installation, suggesting that similar devices should be installed in HVAC systems to avoid biological risk to people inside buildings. Microbiological tests were carried out to verify the germicidal effect, analyzing the viability of microorganisms circulating in the environment. One of the greatest advantages of this type of installation is that the lamps were completely covered, avoiding any risk of hazardous exposure to people and animals. Six 15 W low-vapor-pressure mercury lamps emitting 253.7 nm UVGI were installed in the ducts of the fan coil, maximizing their luminous interaction in the air passage. As a test for the future dissemination of UVC light installations to improve indoor air quality in Hospitals in Sergipe State, Brazil, we made a first installation of UVGI disinfection lamps, strategically placed in the Heating, Ventilating, and Air Conditioning (HVAC) system of the Intensive Care Unit (ICU) at the University Hospital of Lagarto, Federal University of Sergipe, Brazil. Recently, the World Health Organization recognized that the COVID-19 virus could be transmitted across large distances, suggesting that indoor ventilation is key in airborne transmission. Thus, UVC can improve indoor air quality by controlling bioaerosols and can be used as an engineering device to interrupt the transmission of pathogenic organisms and potential bioterrorism agents. UVC inactivates a wide range of microorganisms by damaging the structure of nucleic acids and proteins at the molecular level, so they become unable to replicate and cause disease. Ultraviolet germicidal irradiation (UVGI) uses short-wave ultraviolet (UVC) light to inactivate organisms like viruses, bacteria, and fungi.
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