... bearing, high-strength, low noise, durable;3. Using air downstream principle, pvc shutter or aluminum shutter, antioxidant, ... , open and close sweetly, prevent backflow of air; 4. High-strength more high-gluten strength aluminum ... two types of fan house, slant wall type, upright wall type, could satisfy varieties need of different ... :IP55, insulation class: F grade. air cooling system for poultry house