In 2000, ARC-FLASH was the first to overcome the limit of only UV light being able to activate Photocatalyst and successfully developed “visible light responsive” feature working with both the ultraviolet of 300~400nm wavelength and the visible light of 400~800nm. Thus ARC-FLASH started a new era of “visible light responsive” Photocatalyst. In the past, Photocatalyst could only be triggered by ultraviolet light, which confined the application of Photocatalyst. It became necessary to install ultraviolet lighting tube if there was no such light in order to inspire Photocatalyst for reaction. But now, even in an environment lack of natural light or at night, it can also use visible light (fluorescent lamp or bulb) for reaction since the fourth generation Photocatalyst increases the applying range and cut the cost of adding illuminating devices.