Germicidal UV Lights

 Germicidal UV Lights (UVC) used for UV disinfection inactivates microorganisms by disrupting their cellular membranes and by damaging their DNA or RNA. The UV light initiates a reaction between two molecules of thymine, one of the bases that make up DNA. UV light at 253.7nm wavelength (germicidal UV or UVC) causes adjacent thymine molecules on DNA to dimerize. The thymine dimer is very stable. If enough of these defects accumulate on a microorganism's DNA its replication is inhibited, resulting in effective UV disinfection by rendering the microorganisms harmless. 

 The longer the exposure to UVC light, the more thymine dimers are formed in the DNA. If cellular processes are disrupted because of DNA damage, the cell cannot carry out its normal functions and can not reproduce. Microorganisms that can not reproduce can not cause diseases. If the damage is extensive and widespread, the cell will die. 

  Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. UVGI is used in a variety of applications, such as food, air, and water purification.

UV-C light is weak at the Earth's surface as the ozone layer of the atmosphere blocks it. UVGI devices can produce strong enough UV-C light in circulating air or water systems to make them inhospitable environments to microorganisms such as bacteria, viruses, molds and other pathogens. UVGI can be coupled with a filtration system to sanitize air and water.

The application of UVGI to disinfection has been an accepted practice since the mid-20th century. It has been used primarily in medical sanitation and sterile work facilities. Increasingly it has been employed to sterilize drinking and wastewater, as the holding facilities are enclosed and can be circulated to ensure a higher exposure to the UV. In recent years UVGI has found renewed application in air purifiers.