|Passive filters. These inexpensive disposable
filters, purchased in hardware or a variety of other stores, have
the ability to block only the large particles from passing through
the filter. The limited success of these filters is based on the size
of the mesh.
Frictional electrostatic filters. These relatively
high-priced, reusable "tron" filters use material that
is supposed to create a static charge when the air passes through
the filter. Although these filters can remove smaller particles
than the passive filters when clean, dust accumulation and humidity
easily neutralize the relatively small electrical charge.
Electronic precipitators. These are expensive to
purchase, install, operate, and maintain. These systems give particles
a positive charged field created by high voltage wire elements.
These charged particles are supposed to be attracted to polarized
metal plates. However, as particles build up on the plates, particle
collection capability diminishes. These highly charged particles
escape capture by the plates and return to the air space where they
precipitate out onto the interior surfaces resulting in dirt buildup.