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
re circulated 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
humidistat's, are difficult to service and may
require a heating specialist. If there is a lot
of corrosion on the unit, it should be serviced. |
