There are 3 main types of UV ray, they are UVA, UVB, and UVC. Because UVC rays have the shortest wavelength, and therefore highest energy. They are capable of killing pathogens like bacteria and viruses. The UVC light with a wavelength of between 200-280nm, is highly effective at decontamination because it destroys the molecular bonds that hold together the DNA of viruses and bacteria, including "superbugs," which have developed a stronger resistance to antibiotics.
According to International Ultraviolet Association, it is believed that correctly using UVC light can help prevent Covid-19 transmission by reducing contamination based on existing evidence and knowledge about viruses. Having said that, when using UVC devices, skins and eyes should not be irradiated by the UVC light. Especially when using a conventional low-pressure germicidal lamp, no one should stay in the area when sterilization starts.
Nowadays, the UVC technology has advanced to a fourth generation by using light emitting diodes (LED) to emit ultraviolet light. The use of this technology can be adjusted in order to produce short-wave ultraviolet. According to a research supported by the EPA (Environment Protection Agency) of USA, it is concluded that UVC LEDs are effective for inactivating bacterial and viral pathogens. The advantages of this emerging technology are: long service life of LEDs, low temperature and low energy consumption, no heat radiation, no unwanted toxic substances, immediate full function without preheating and shorter disinfection time.
Recently, the CNN News reported that the agency in charge of public transit in New York City announced a pilot program using ultraviolet light lamps to kill Covid-19 on buses and trains and at stations. Also, David Brenner, the director of the Center for Radiological Research at Columbia University, reported his test showed UVC light successfully eliminated the virus that causes Covid-19.
Environment Protection Agency
International Ultraviolet Association