FFU (Fan Filter Unit) is the combination of the Fan and Filter, also known as "filtering equipment of the air blower. Head is usually installed in the clean room terminal air supply, usually placed in the hoisting of the "dry" gasket seal on the keel frame. Above the head part is fan module, the following sections for the filter. According to the requirements of cleanliness, the filter can provide different levels of efficiency (HEPA) or super efficient (ULPA) filter, clean air for clean room. Fan module in addition to overcome the resistance of the hepa filter head lower, but also overcome the resistance of the entire circulation wind all components of the channel, so as to maintain a set of wind speed operation. Flexible head system had advantages of simple design and construction, wind speed regulating, clean area is easy to change wait for a characteristic, therefore has become one of the popular industrial clean room system.