1.poultry farm ventilation fan 2.large air permeability 3.low noise 4.different size ventilation fan 1.Frame : The frame ... alloy, hot casting molding, light weight, high strength, and good tension.3.blade : Six new design stainless steel blades were made ... frame, no deformation, long service life, the use of belt tension inside, effectively prevent reverse twist of belT 8.Eight strict ...