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Mechanical air purification is one of the 3 major
methods to clean the air in your home.
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Air purification can be effective if appliances are regularly maintained
Mechanical filters may be installed in ducts in homes
with central heating and/or air-conditioning or may be used
in portable devices which contain a fan to force air through
the filter. Mechanical filters used for air purification are of
two major types.
Flat or panel filters generally consist either of a low
packing density of coarse glass fibers, animal hair,
vegetable fibers, or synthetic fibers often coated with a
viscous substance (e.g., oil) to act as an adhesive for
particulate material, or slit and expanded aluminum. |
Flat filters may efficiently
collect large particles, but remove only a small percentage of respirable size particles.
Flat filters may also be made of "electret" media, consisting of a
permanently-charged plastic film or fiber. Particles in the air are
attracted to the charged material.
Pleated or extended surface filters generally attain greater
efficiency for capture of respirable size particles than flat
filters. Their greater surface area allows the use of smaller fibers
and an increase in packing density of the filter without a large
drop in air flow rate.
Because higher efficiency pleated filters
are much thicker than filters generally used in standard home
heating and/or air-conditioning systems, their use results in
substantial air resistance, so they cannot be directly incorporated
into the standard residential system. Instead, a system must be
specially designed with a fan of sufficient power to create the
necessary air pressure and with one or more efficient pre-filters
Costs for installation of the system, replacement of pre-filters and
filters, and system operation should be considered before deciding
whether to purchase higher efficiency filters
The basis types of air purification systems
Cost and maintenance requirements should be
a key consideration when you explore what type of air filters you
are going to select. The basic types of air filters include:
Panel filters
Panel filters are
inexpensive to buy-they cost between 50 and $5-but they have
dust-spot efficiencies of less than 5%. Their filtering capability
actually increases as they get dirty, but this is accomplished at
the expense of restricting air flow and increasing pressure drop. To
avoid restricting air flow, they should be changed every one to
three months. They do a poor job of protecting the forced-air system
and offer human lungs almost no protection from particles.
Electrostatic
air filters
Electrostatic panel filters are a little
more effective than standard panel filters because they rely on
static electricity to attract charged particles in the airstream.
Either the static electricity is created by air as it flows through
the filter, or the filter is manufactured with precharged electrets
made from a propylene, polypropylene, or other plastic material. The
electrets are permanently charged with both positive and negative
charges. As air flows past the charged filter material, oppositely
charged particles in the airstream cling to the filter's fibers.
High-Efficiency
Particulate Air Filters (HEPA)
High-efficiency particulate air (HEPA)
filters achieve the maximum efficiency available, with dust-spot and
DOP test values greater than 97.99%. However, HEPA filters greatly
restrict air flow and require special blowers and duct design. They
are usually found in "clean room" applications in industrial or
commercial settings, rather than residences
Extended surface
filters
An electronic air cleaner, or
electrostatic precipitator, uses high voltage to charge particles in
the return airstream. The charged particles are collected on an
oppositely charged metal plate. Electronic air cleaners achieve
dust-spot efficiencies of over 90% with little air flow restriction
  5
star product As it is not clearly evident that air
duct cleaning has a lasting effect on improving indoor air quality,
we suggest that you consider an easy and economical solution that
combines air ionization technology, ozone air cleaning, and UV
germicidal protection.
Air purification details.
A great resource from the college of NC State university college of
agricultural and life sciences on air filter technology and what to
look for in air cleaners.
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Articles and
related resources |
User input and experiences with various manufacturers products are
posted here and can be sorted and searched by price range,
manufacturer, and number of reviews. Once you've decided on a
type of air cleaning system, this is a great place to check out
consumer reviews.
A great resource site of information on radon, smoke, mold, and
indoor air quality problems.
The ALA provides a detailed fact sheet of credible scientific
evidence on a host of indoor pollutants like radon, carbon monoxide,
ozone, and particulate matters.
Read about a study underway to determine the roles of other key
environmental agents in asthma, both in bringing on respiratory
crisis and initiating the illness in the first place - early
evidence is pointing to indoor pollutants playing a key role.
This USDA study concluded that "the effectiveness of the
ionizers for removing dust suggests that this type of system has
good potential for reducing airborne transmission of disease".
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Search for air purifiers, filters, and air indoor air quality issues here |
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