|If you have forced hot air heating or cooling,
furnace filters protect your furnace's motor
and fan from grit and contamination, and
they also prevent unwanted dust and other
airborne particles from continually circulating
through your house.
How much the filter traps and how small the
types of floating elements it captures are
determined by the filter. What are the choices?
- Standard furnace filters are fiberglass meshes generally about an
inch thick and remove the big stuff like
hair, dust, and dirt. They cost no more than
a few dollars apiece and need replacement
less often than other filters because they
trap less material and start with a higher
air flow rate.
- Pleated filters remove from a third up to 99% of all airborne
particles including the ones like pollen
and mold that trigger common allergies. Pleated
filters increase the surface area that strains
the air while decreasing the rate the air
moves through it due to improved filtering.
High efficiency filters have an electrostatic
charge that pulls more from the air than
regular pleated filters. Depending on the
size of the particles they remove, these
filters can be up to ten times the cost of
a standard filter.
- Electrostatic filters or electronic air cleaners, which pass the air between two electrically
charged plates that pull contaminates toward
them, take about 95% of all airborne particles
out of the air. As a side effect of the electronic
Cost varies from a few to several hundred
charge on the plates, these filters produce
small amounts of ozone, a mild irritant.
- High Efficiency Particulate Air (HEPA) filters remove virtually everything from the air.
These filters allow only very small particles
(less than one-thousandth of an inch) to
pass, but require their own fan and filter
assembly at a significantly greater cost
than any of the other options.
When choosing a filter, remember that air
filters collect particles onto themselves
and so need to be cleaned or changed periodically.
Be sure to compare the cost and effort of
cleaning and changing when comparing prices.