The human’s eyes perceive electromagnetic waves with wavelengths between 400nm to 760nm, but the ultraviolet light wavelength is shorter. It is about 100nm to 480nm.Ultraviolet light is divided into three regions. UVA：315nm-480nm，UVB:280nm-315nm, UVC: 100nm-280nm. UVC wavelength kill most of virus and microorganism in the air and water, and make them unable to reproduce.UVC is physics method for the sterilizer，it doesn’t add other materials. Compare the chemical reagent disinfection method, the ultraviolet light is more environmental protection and safety.