... poultry farm ventilation fan 2.large air permeability 3.low noise 4.different size ventilation fan 1.Frame : The frame ... fracture, attractive and durable. The angle is reasonable, so small noise and big wind capacity,4.shutter: made of high strength ... prevent reverse twist of belT 8.Eight strict quality testing; noise testing, vibrationtesting, static balance testing, dynamic balance testing, turning ...