Ventilators Axial fans. Axial fans. “Klima” fan with grill guard. Walking grits on top of fans. Number of fan blades variable. Number of blades depending on back pressure. Beside blades, diameter is also important for air and pressure. More blades (up to 10) for higher backpressure. Plan of cel with fans on 80% capacity. Fans setup page. Fan status: off – stand-by – on – alarm/failure. Anti-backflow valves for fans. Example one open and one closed. Valves in equilibrium. Valves open at start of fan. Vertical air circulation. Horizontal air circulation. Easy to move. Intensive circulation along bags and through bins and crates.