The Air Innovations model 505 ultrasonic, cool mist, smart humidifier is one of the top rated, longest running, and most versatile humidifiers available for its size. Key Features: 1.37-gallon tank that runs for a full 70 hrs. on low (almost 9 nights of Permanent ceramic filter never needs replacementprovides moisture for up to 70 hours when set on lowPowerful enough to add humidity to large rooms up to 400 SQ ft., with a programmable built in humidistat that monitors and maintains the humidity level you setThe entire unit and base are made of antimicrobial plastic to prevent bacteria, mold, and mildew growth and it comes with a permanent ceramic filter to help trap impurities in your water.Digital LED DisplayAdjustable humidistat