Ultraviolet germicidal irradiation

Ultraviolet germicidal irradiation (UVGI) is a disinfection technique employing ultraviolet (UV) light, particularly UV-C (180–280 nm), to kill or inactivate microorganisms. UVGI primarily inactivates microbes by damaging their genetic material, thereby inhibiting their capacity to carry out vital functions.^[1]

The use of UVGI extends to an array of applications, encompassing food, surface, air, and water disinfection. UVGI devices can inactivate microorganisms including bacteria, viruses, fungi, molds, and other pathogens.^[2][3] Recent studies have substantiated the ability of UV-C light to inactivate SARS-CoV-2, the strain of coronavirus that causes COVID-19.^{[4][5][6][7][8][9]}

UV-C wavelengths demonstrate varied germicidal efficacy and effects on biological tissue.^[9][10][11] Many germicidal lamps like low-pressure mercury (LP-Hg) lamps, with peak emissions around 254 nm, contain UV wavelengths that can be hazardous to humans.^[12][13] As a result, UVGI systems have been primarily limited to applications where people are not directly exposed, including hospital surface disinfection, upper-room UVGI, and water treatment.^[14][15][16] More recently, the application of wavelengths between 200-235 nm, often referred to as far-UVC, has gained traction for surface and air disinfection.^[11][17][18] These wavelengths are regarded as much safer due to their significantly reduced penetration into human tissue.^{[19][20][21][22]} Moreover, their efficiency relies on the fact, that in addition to the DNA damage related to the formation of pyrimidine dimers, they provoke important DNA photoionization, leading to oxidative damage.^{[23] [24][25][26][27]}

Notably, UV-C light is virtually absent in sunlight reaching the Earth's surface due to the absorptive properties of the ozone layer within the atmosphere.^[28]