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air cleaners
typically employ filters, electrical attraction, or
ozone, and range in price from $60 to $500. A
good filter will provide five air changes per hour per
room. A very efficient collector with a low air-circulation
rate will not be effective, nor will a less efficient
collector with a high air circulation.
HEPA,
or High-Efficiency Particulate Arresting filters, capture
up to 99.97 percent of air particles of 0.3 microns
or larger. A fan pulls air through a foam pre-filter
to remove large particles. Air is then forced
through the HEPA filter, which removes most other particles.
Although they are highly effiecient and require little
maintenance, these filters use a power fan to push air,
and the fan increases energy costs and noise.
Because HEPA-type filters are similar to HEPA filters
in style but use a more permeable paper, they are less
expensive, and less efficient, than HEPA filters.
ULPA,
or Ultra-Low Penetrating Air filters, newcomers to residential
air cleaning, remove 99.99 percent of airborne particles
as small as 0.1 micron. This type of filter is
a favorite in hospitals.
Electrostatic
Precipitators deliver a negative electrical charge
to particles that pass through them. The particles
are then attracted to a positively charged collector
that must be cleaned frequently. Precipitators
are said to be 95 to 99
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percent
efficient and have low energy and filter costs, but
their efficiency decreases with use. They also
can produce a small amount of ozone.
Electrostatic
Air Cleaners also rely on electric charges to clean
the air, and when clean, are highly efficient.
They are cheap and do not produce ozone, but they are
not as efficient as precipitators.
Ozone
Generators are not proven effective at air cleaning.
While ozone can purify drinking water, it is a toxic
gas with no known beneficial health effects. Both
Consumer Reports and the Environmental Protection Agency
advise against using ozone-type air cleaners.
HVACs,
or Heating, Ventilating, Air Conditioning systems, cannot
be installed if your house employs radiators for heat.
In-duct air cleaners for existing HVAC systems run from
$250 to $800. Keep in mind that these systems
can serve as a conduit for pollutant sources from the
outdoors, and, if improperly maintained, can act as
breeding grounds for molds and bacteria. Every
HVAC system contains a filter in the return air stream
that must be changed or inspected monthly. Dirt
collection in an HVAC system serves as a nutrient to
microbial growth. If moisture collects, molds
and mildews grow.
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