Electrified fibrous air filters

THERE are two principal methods of separating suspended particles from air: mechanical separation and electrostatic precipitation. Mechanical separation includes dry-type filters, cyclones, water scrubbers, and gravity settling chambers. Dry-type filters are commonly used in air conditioners. Mechanical separators depend on inherent differences in size and density existing between particles and the gas in which the particles are suspended. In contrast, electrostatic precipitators cause a difference between properties of particle and gaseous medium; that is, either the particle is charged in an ionizer1 or, without an ionizer, the particle undergoes polarization in the field existing between charged plates of the precipitator.