An air ionizer is built around a negative ion generator. This generator sends out a stream of negative ions that attract positive airborne dust and allergen particles in the air. As a result, these particles become too heavy to remain airborne and fall to the floor. As the majority of surfaces in a room are positively charged, the particles from the ionic air are attracted to these surfaces as well. This means that the area around the ionic filter tends to get dark spots on nearby walls and floors. Some ionizers however, have special electrostatic precipitators which trap particles on a metal plate. To remain effective, these plates need to be cleaned regularly.
Ionizers are a relatively inexpensive way to clear second hand smoke. However, if you have a problem with dust or pollen an ionizer air purifier may not be the best choice because the particles are not completely eliminated. The main health concern related to ionic air purifiers is the fact that they produce ozone as a byproduct. When ozone is inhaled directly into the lungs, it can pose a health risk. The EPA classifies ozone as a toxic gas that causes lung damage, triggers asthma attacks, and can even lead to increased risk of death. These are all facts that need to be taken into consideration when purchasing the right air purifier.