DID YOU KNOW indoor air can be more polluted than outdoor air? The NUK® HEPA-Type Air Purifier removes 99% of airborne particles - allergens, dust mites, pollen, pet dander, etc. - to create a healthy environment all day and all night long. Purifier emits a soothing white noise, which is significantly more effective at getting infants to sleep quickly versus silence. Child-Resistant Plug Lock catches and holds the appliance plug so that child cannot easily tug it out of the outlet. The soothing amber nightlight is better for sleep than blue or white nightlights, which depress production of the sleep hormone melatonin. Permanent HEPA-Type Filter never needs to be replaced: simply vacuum when maintenance light illuminates - every 3 to 4 months. Optional Ionizer emits negative ions that bind with airborne dust and pollen to form larger particles that are easily captured. 3 year warranty.