Breathing Clean:
How Air Filters Provide Cleaner Living

Indoor air quality can be a problem
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People spend up to 93% of their time indoors where - suprisingly - air
pollution can be up to 10 times greater than outdoor levels. This poor
indoor air quality results from reduced natural ventilation - a
phenomenon that has developed in recent years from tighter, more energy
efficient building construction.
Indoor air consists of mostly invisible gases and particulates,
including many which can be characterized as pollutants. These
pollutants include many substances taken for granted, such as cooking
smoke and grease, aerosol sprays, tobacco smoke, animal dander, ashes,
human skin flakes, household cleansers, carbon dioxide, viruses,
bacteria, pollen, and fungi.
Fortunately, there is a way to have cleaner, fresher air, and that's
by using air filters in your air conditioning and/or heating system.
This phamphlet addresses particulates, non-pollutant gasses, which can
have both short-term and long-term effects on life style and quality.

What air filters do
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Air filters remove particulates before they soil furnishings, foul
critical system components, cause discomfort, or otherwise spoil a
comfortable indoor environment. As air is drawn to the central forced
air system, it passes through the filter where particles of dirt and
dust are trapped. The filtered, comfort conditioned air is then
recirculated back through the home.
Consumers have a choice of three types of air filters: Standard
filters, media filters, and electronic air cleaners. Each type
differs in cleaning efficiency and costs. Portable air filters are
also available for small area use. Some employ highly efficient
HEPA (High Efficiency Particulate Air) filters which were previously
used for specialized purposes, such as medical operating rooms. Your
heating and air conditioning contractor or dealer can recommend which
should be best for your home and your family's particular needs.

How much filtration do you need?
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Standard filters such as the throw-away fiberglass and washable
metal mesh filters are the least expensive of all air filters. They
are designed to catch only the larger and more visible particles of
dust and dirt that circulate through a forced air system. These
filters should be checked every two months - and every 30 days during
peak use of extensive indoor activity.
Those filters that can't be removed and cleaned with water should
be replaced. Disposable fiberglass filters are relatively inexpensive;
most common sizes are available at hardware stores, drug stores,
builder supply outlets, and convenience stores. Their efficiency is
about 3 to 5 percent according to standard industry comparisons.
(ASHRAE Standard 52.1-1992 "Gravimetric and Dust-Spot Procedures for
Testing Air-Cleaning Devices Used in General Ventilation for Removing
Particulate Matter").
Media filters are more effective than standard filters, but also are
more expensive. They can remove very small particles that require an
optical microscope to be seen individually - such as pollen, lint, dust
plant spores, cooking grease, and some tobacco and cooking smoke.
The filtering material must be replaced at least annually - the
homeowner removes the old material and discards it. The new filter
material, available from heating and air conditioning contractors, is
then positioned and inserted according to manufacturer's instructions.
efficiency is about 25 to 35 percent.
Electronic air cleaners, the most expensive of all air filters, also
are the most efficient as shown on the following panels.

Electronic air cleaners remove up to 95% of dirt, dust, smoke
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Electronic air cleaners are by far the most efficient cleaners of
indoor air. Unlike standard or media air filters that merely get in
the way of relatively large particles, electronic air cleaners attract
and retain pollutants like a powerful magnet. Using electrostatic
precipitation principles, they are even effective on particles so small
that an electron microscope would be required to see them.
While the larger particles of dirt are trapped by the screen
prefilter, the smaller microscopic particles (as small as one micron)
pass through an ionizing section where they receive an electrical
charge that traps them on the charged collector plates. Electronic
air cleaners are 10 to 20 times more efficient than standard filters
as they remove up to 95 percent of the dirt, dust, and smoke that
otherwise circulate through the air.
Electronic air cleaners also are energy efficient - most require no
more power per day than a 40-watt light bulb. They feature permanent
aluminum "cells" that can be rewashed in a dishwasher or laundry tub
and reused almost indefinitely. Electronic air cleaners are available
from air conditioning and heating contractors; builders can install
them in new homes or remodeling projects.

Electronic air cleaners give particles a charge
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Unlike standard or media air filters that merely get in the way of
relatively large particles, electronic air cleaners attract and retain
pollutants like a powerful magnet. Millions of airborne dust, smoke,
and pollen particles are carried through the return air ducts to the
electronic air cleaner. When they reach the unit the larger particles
are trapped by a screen prefilter. Smaller particles pass through to
the ionizing section where they receive an electrical charge. These
charged particles continue through the cell to the collecting area
where they are attracted to a series of grounded plates. The
pollutants are held in this section until washed away during cleaning.

Particles caught by three air filters: standard, media, electronic
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Electronic air cleaners effectively capture a wide spectrum of
minute airborne pollution particles measured in microns (one 25,400th
of an inch).
Air cleaning efficiency varies with particle size. The efficiency
of residential standard filters decreases rapidly on particles below
100 microns, and they are virtually ineffective on particles below 10
microns. Media air filters are 5 to 10 times more efficient than a
standard filter, virtually 100% effective on particles above 10
microns, and effectively remove most dirty air particles down to 0.5
micron. Highest efficiency is achieved with electronic air cleaning,
which effectively removes particles down to 0.01 micron, so small an
electron microscope is required to see them.

Clean filters and other money savers
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Keep filter clean. For any filter to work efficiently, it must be
cleaned or replaced from time to time. Dirty filters add up to more
money for the consumer because they force the heating/cooling system
to circulate air while pulling it through a clogged and dirty filter.
As previously explained, most filters can be easily inspected and
cleaned or replaced by homeowners.
Let contractors help. Air conditioning contractors also will
check filters as part of preventive maintenance that is well worth its
cost. This includes checking worn parts, such as belts and electrical
contacts; making sure that the thermostat is working properly; and
replacing or adding refrigerant if needed.
Adjust thermostat properly. Another method of increasing efficiency
includes installing thermostats which automatically raise and lower
home temperature for prescribed periods to save energy. This also can
be done with conventional thermostats. However, when you want to
achieve rapid temperature change for comfort, don't set the thermostat
higher or lower than the desired temperature. That doesn't cool or
heat the home any faster - it just makes the system work longer.
Keep doors and windows shut. Whenever a cooling or heating system
is working, doors and windows should be shut - the system can't be
helped by making it easier for outside air to flow into the house.
When the freshness of outside air is wanted, turn off the air
conditioning or heating unit first.
Manufacturers of residential air conditioning and heating systems
want consumers to know everything they can about achieving maximum
comfort and efficiency while saving energy and money, too. If you
have questions about your present system or how to improve it, call in
an expert - a local air conditioning contractor such as those listed in
the Yellow Pages of your telephone directory.