Ionizers are devices that use negative ions to remove small particles from the air, helping to reduce odors and make the air appear fresher. This is achieved by electrostatically charged plates that produce negatively charged ions. These ions attach to small airborne particles, such as cigarette smoke and other toxins, as they move through the air. Ionizers are used in air purifiers to remove particulates from the air, as particles suspended in the air become charged by attracting charged ions from the ionizer by electrostatic attraction.
The particles are then attracted to any nearby grounded conductor, either by plates deliberately placed inside an air filter or simply by the nearest walls and ceilings. The National Health Service (NHS) in Britain conducted a study to investigate the effectiveness of anions in purifying the air. This was due to a high frequency of nosocomial infections in hospitals. The results showed that installing a negative air ionizer eliminated repeated Acinetobacter infections transmitted through the air in a ward, resulting in a zero infection rate. A manufacturer has also discovered that positive and negative ions produced by air conditioning systems can inactivate viruses such as the flu. Bipolar ionization (also known as bipolar needle-tip ionization) is an air cleaning technology that disperses positively and negatively charged ions in a space. The principle of operation of an air ionizer involves a special emitter that creates an ionizing field through which dirty air passes.
Ionization decreases dramatically with distance (even in ducts), so air ionization is rarely used for this purpose, and only for elements immediately adjacent to the actual ionizer.