An air purifier is a device which removes contaminants from air. Air purifiers are commonly marketed as being particularly beneficial to allergy sufferers and asthmatics, and at reducing second-hand tobacco smoke.

Dust, pollen, pet dander, mold spores, and dust mite feces can act as allergens, triggering allergies in sensitive people. Smoke particles and volatile organic compounds (VOCs) can pose a risk to health. Exposure to various components such as VOCs increases the likelihood of experiencing symptoms of sick building syndrome.[1] Air purifiers are used to reduce the concentration of these airborne contaminants and are especially useful for people who suffer from allergies and asthma[2]. They also reduce the need for frequent household cleaning. Air purifiers use a small amount of electrical energy, causing a small amount of expense and environmental effect.EOT;