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Indoor air pollution is a growing concern.
These air contaminates may include:
- Solids (dust, fumes, smoke)
- Liquids (mist)
- Gases (carbon monoxide, hydrocarbons)
The job of the filter is to trap some of
these contaminates and other airborne particles, prevent them from
passing through the system (damaging the unit), collecting on the
blower, and being recirculated into the air. The average residential
filter traps only the solids.
There are several types of filters available:
Disposable filters
- Adhesive filters are very common. The
fibers are usually coated with an adhesive to help trap dust.
- Disposable filters come in many styles
and are made from a variety of materials including, glass, cotton,
and synthetics.
Maintenance should include: Replacing the
filters as they become clogged, usually a minimum of twice a year.
If there are pets or plants in the house, the frequency may increase.
Hold a bright light up to the filter to look for heavily loaded
areas, or any holes in the filter itself.
Washable or reusable filters
- Washable, includes aluminum, synthetics
(many different styles available). Stay away from frame-less filters,
they are susceptible to failure, and can be sucked into the plenum,
and allow dirt to bypass. Some washable filters are adhesive as
well. A spray can be utilized to enhance the adhesive coating.
- Pleated or deep pocket type filters,
allow for a larger filtering surface, some are reusable and others
are disposable.
- Hepa filters, resemble a coffee filter
material. These are very efficient for collecting particles in
the air.
- Electrostatic filters use a passive charge
to attract and hold the particles. Some may restrict air flow
a cause a pressure drop across the coils.
Electronic air filters:
These filters are a very effective method
of cleaning the air. As air passes to the filter it usually passes
through a pre-stage filter that traps larger particles. The air
then moves to the electronic filter where it passes through a highly
ionized field. A series of wires puts a high positive voltage on
the particles as they pass through the field. The particles are
then attracted to the negative grounded plates.
Maintenance should include: Cleaning every
few months. Most washable filters can be put in a dishwasher or
hosed off. Check to see what the manufacturer recommends.
These filters however, are not always successful
in removing odors and other gases. There are a number of specialty
filters available which include:
- Carbon (removes odor and bacteria)
- Ultraviolet light (ozone producing, which
kills bacteria)
HUMIDIFIERS
With a forced air heating system, the air
in the house may become very dry. This can be uncomfortable to the
occupants in the house, and be related to dry skin and difficulty
in breathing. The relative humidity should be around 35%. Low humidity
can also dry out wood-work, furniture, and other possessions in
the house. Humidifiers add water vapor to the air. They can be introduced
directly into the heating ductwork, or be an entirely independent
system. Excessive humidity may cause mildew and molds to form. The
humidity level is controlled by a humidistat.
There are several styles of humidifiers:
- Drum
- Mist
- Evaporation
- Electric
Maintenance may include: Annual service
and cleaning. Hard water or well water may make frequent cleaning
necessary. The nozzles and drains are susceptible to clogging, and
the floats should be checked for sticking. If the reservoir is allowed
to overflow, the water could back into the furnace and cause damage
and corrosion. Some humidistats, are difficult to service and may
require a heating specialist. If there is a lot of corrosion on
the unit, it should be serviced.
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