Two of the most common types of air cleaners are the electrostatic precipitators and the particulate filtration units. Electrostatic precipitators attract particles to filters or plates by establishing opposite electrical charges. The first stage generates positive ions, which become attached to the particles in the airstream. In the second stage, the resulting positively charged particles are collected on negatively charged plates. Particulate filters use porous pads of different materials such as wire, glass, or hemp.
Gases pass through the filter, but most particles are trapped.
Particulate filters usually are less expensive than electrostatic precipitators. Either type of filter can be used in conjunction with a forced air duct system or as an individual unit in rooms. An air cleaner unit must be large enough to handle the volume of air in the room or home where it is to be used. Also, air cleaners require regular maintenance to perform properly. The January 1985 issue of Consumer Reports rates the effectiveness of several types and models of home air cleaners.