Vornado Evap40 4-Gallon Evaporative Humidifier Humidifies up to 1,000 sq. ft. through the use of signature vortex circulation. Hertz - 60 HZ. The high speed RPM is 1600 and the low speed RPM is 750 RPM Adjustable humidistat for automatic humidity control and 3 speed settings (low, medium, high) 4 gallon capacity and up to 4 gallon output every 24 hours for long, uninterrupted operation Airlock water tanks are easy-to-fill, spill-proof and leak-free. Product Dimensions-19.50 L x 10.50 W x 13.50 H Inches Simple to clean, assembled in the USA and backed by a 5-year limited warranty