Direct drive centrifugal fan with long working time, Low noise, maintenance free, small vibration and step less speed regulation. Its life time is more than 30,000h. The speed regulation is reliable. The air flow is still the same when the HEPA filter works at final pressure. The ideal solution for class 100 application of high cleanliness product assembly line, equipped w/ US DYWER with clear instructions of both sides pressure and informs of HEPA filter renewal.