Most natural UV light is generated by the sun with about ten percent of sunlight being UV and only about three to four percent penetrating the atmosphere to reach the ground. Of the UV radiation that reaches the earth, 95 percent is UVA and five percent is UVB.

No measureable UVC from the sun reaches the earth's surface. Because of the spectral senstitivity of DNA, only the UVC region demonstrates significant germicidal properties.

UVC LED IS THE FUTURE

In the case of disinfection, the optimum wavelength is in the region of 260 nm to 280 nm, with germicidal efficacy falling exponentially with longer wavelengths. UVC LEDs offer considerable advantages over the traditionally used mercury lamps, notably they contain no hazardous material, can be switched on/off instantaneously and without cycling limitation, have lower heat consumption, directed heat extraction, and are more durable.

As a solid-state device, UVC LEDs can be cycled on/off tens of thousands of times with little or no observable difference in degradation performance. In addition, UVC LEDs offer a near instant capability to provide its full rated output, requiring no warm-up time. These abilities mean that LEDs can be used in an on-demand fashion, accumulating operating hours only when “on” and providing their disinfection function without penalty.