Suitable for domestic, commercial or industrial applications. Heavy-gauge, spun steel housing with baked epoxy finish with external junction box contains connections. Backward curved blades to ensure the lowest possible sound and to develop ample static pressure. Durable external rotor motor provided with thermal reset overload protection. Ball bearing motor, permanently lubricated for maintenance-free operation and continuous running. Fan and motor assembly balanced for quiet and vibration-free operation with variable speed control. 5 year warranty.