You may be confused about the difference between a humidifier and an air purifier. While they sometimes do similar jobs, they are actually completely different appliances.
Air purifiers are machines designed to clean the air inside a specific room or in an entire house. They can remove dust, pollen and allergens to make the air more easily breathable for people who have allergic reactions or who live in smoggy areas.
Good air purifiers work by pulling air through a High Efficiency Particulate Air (HEPA) filter, which cleans it of any particle larger than one-tent of a micrometer—pretty small indeed. Other techniques to clean air include passing it under ultraviolet light to kill any microorganisms that might exist in it.
Air humidifiers, by contrast, are designed to make the air wetter and more humid. These devices can reduce the amount of dust in the air—which is why they're often confused with purifiers—though this isn't their main function.
They work by releasing water vapor or steam into the air, moistening it. This is ideal for families that live in hot, dry areas as it helps prevent dry skin and cracked lips.
Humidifiers can also help prevent property damage associated with dryness, such as wood warping and paint cracking.