Panel fans mount to an exterior wall of a building and help maintain indoor air quality to allow occupants to breathe comfortably. Also known as sidewall propeller fans, these fans are suitable for ventilating factories, warehouses, light manufacturing plants, schools, storage facilities, and other indoor areas where fans cannot be mounted to the ceiling. They also may help regulate the indoor air temperature since they circulate the air. Panel exhaust fans pull stale air, heat, odors, and some moisture out of indoor spaces to reduce airborne contaminants. Panel supply fans continuously pull fresh air into indoor spaces to allow occupants to breathe comfortably. Reversible panel exhaust and supply fans have a switch that allow them to be used for both exhaust and supply applications.