Researchers at Hiroshima University found that Ultraviolet C light with a wavelength of 222 nanometres is safe for use around humans and also effectively kills SARS-CoV-2. This is the first research that proves its efficacy against the virus.
Other studies that involved studying 222nm UVC have so far established its potency to eradicate seasonal coronaviruses but not COVID-19. The researchers in the in-vitro experiment revealed that 99.7% of the SARS-CoV-2 viral culture was killed after a 30-second exposure to the UVC 222nm radiation at 0.1mW/cm2.
The tests were conducted using Ushio’s Care222TM krypton-chloride excimer lamp. UVC light at wavelength 222nm cannot penetrate the outer (non-living layer) of the skin and human eye so it won’t cause harm to the cells living beneath, which makes it a safer alternative to the more damaging 254nm UVC.
The 222nm wavelength of UVC can be a promising disinfection system for public spaces and hospitals where there is a possibility of nosocomial infections.
Ref link: https://www.ajicjournal.org/article/S0196-6553(20)30809-9/fulltext