... , 50Hz 3. Noise: less than 55dB 4. Adjustable Introduction:Fan filter unit (FFU) is air cleaning equipment to supply purified air ... : less than 55dB;3. Power: 220V, 50Hz;4. Highly efficient filter (filtration efficiency is 99.99%);5. Material: armor plate, stainless ... highly-efficient centrifugal air blower;9. Durable, low noise, low vibration;10. Free maintenance. Fan filter unit