Vane-axial fans similar in design and application to tubeaxial fans. The major difference is that air straightening vanes are added either in front of or behind the blades to reduce the circular motion of the air. This results in a more efficient fan capable of operating at a slightly higher static pressure. Typical uses are grain drying, aeration, and sometimes pressure duct air distribution. Centrifugal fans are quieter and can operate at much higher static pressures than axial flow fans.
Centrifugal fans operate by throwing air away from the fan blade tips.
These blades can be forward curved, straight, or backward curved. Centrifugal fans should be used for handling relatively clean air because dirt accumulation on centrifugal fan blades affects efficiency and airflow capacity. Centrifugal fans are commonly used in grain drying and forced air heating systems where high static pressures are required. A ventilating system is used to control the environment. Ventilation capacity is based primarily on the amount of air exchange needed to remove moisture in the winter and excess heat in the summer.