The NUK® Cool Mist Ultrasonic Humidifier refreshes and helps relieve the effects of dry air to create a healthy environment all day, and all night long. Virutally silent operation won't wake sleeping child. The soothing amber nightlight is better for sleep than blue or white nightlights, which depress production of the sleep hormone melatonin. Child-Resistant Plug Lock catches and holds the appliance plug so that child cannot easily tug it out of the outlet. Filter free design means no replacing expensive filters. 1 year warranty.