Downblast exhaust and supply fans feature an intake/exhaust opening that points towards the mounting surface. This design aids in weather resistance and helps to prevent water intrusion into the structure. They are generally used for clean air applications to exhaust stale, warm, or odorous air. Centrifugal downblast exhaust fans use a fan wheel to exhaust air towards the mounting surface. Axial downblast exhaust fans feature a traditional fan propeller and exhaust air towards the fan mounting surface. Axial downblast supply fans utilize a traditional fan propeller and draw air into the structure. Axial downblast reversible exhaust and supply fans can function as either supply or exhaust fans.