A device that generates negative electrical charges attracting airborne particles–including smoke, dust and other allergens–which are then trapped, thus cleaning the air. Ionizers are gaining popularity for improving indoor air quality. It is believed that electrical activity from appliances such as heaters, computers and televisions tend to destroy negative charges. These leave the atmosphere with relatively poor positive charges–contributing to respiratory problems, allergies, headaches and even depression. Ionizers were designed to counteract this effect.