Since the beginning of the coronavirus/COVID-19 pandemic, the use of UVC light as a disinfection method has received widespread attention in the past few months. Moreover, recently, "far ultraviolet lamps" have attracted attention as a safe alternative to traditional germicidal ultraviolet lamps. The difference between far ultraviolet and ultraviolet is their respective position on the electromagnetic spectrum and how much we know about it.
Normally, germicidal UVC light works at a wavelength of 265nm. This particular wavelength of ultraviolet light has been used for decades as a disinfection method, from hospital wards to drinking water. Far-ultraviolet light was discovered at a wavelength of 222 nm. It is a new technology that was tested commercially only last year.
Columbia University released a widely read research report in June detailing their research on light, which is a method of disinfecting the SARS-CoV-2 virus that causes COVID-19. The study found that more than 99.9% of the coronaviruses in airborne droplets were killed by exposure to extreme ultraviolet light. Only a few months later, Far-UVC sterilization products have been put on the market. In September, Japanese lighting manufacturer Ushio Inc. first introduced 222 UV lamp, which they developed with Columbia University together.
As early as March, the FDA issued guidance on UVC disinfection equipment and how it should be used during the COVID-19 pandemic. UVC disinfection is a well-studied method. We know how much UVC light (combination of time and UV radiation intensity) is needed to destroy specific bacteria, microbes and viruses, because it has been used again and again in real life and proved to work.
The main reason why Far-UVC is so attractive is because some people think it is safe for human exposure-unlike UVC light that has been shown to be harmful to the skin and eyes. The Columbia University study found that far ultraviolet light cannot penetrate the tear layer of the eye or the outer dead cell layer of the skin, so it does not damage the living cells in the body. However, if there is no more research to study how humans perform under this kind of light, especially when it comes to long-term health effects, there are still many unresolved problems.