Features and Functions Evaporative humidification with air circulation draws dry air in and pushes moist cool air back into the room 2 ways of water refill: top refill and water tank refill Low water level indicator with auto shut off 1-knob operation Wick filter (included) captures minerals and deposit no white dust Replacement Wick Filter F-4023 (Set of 2) is available for purchase (It is recommended to replace the wick filter every 3 months) 1 gallon (3.7 liters) water tank 3 speeds Essential oil compartment ETL