Which Unit Is Right For
Pollution With Air Cleaners:
Points To Consider For Your Health
Air cleaners are used as one of three methods of reducing
indoor pollutants. In order of effectiveness, the three methods are:
- removal of the source or control of its
- air cleaning
This can be used as an adjunct to source control and
ventilation. However, this method alone cannot adequately remove all of the pollutants
typically found in indoor air.
Should You Use An Air Cleaner?
Many factors need to be considered in determining whether
use of an air cleaner is appropriate in a particular setting. Therefore, the decision
whether or not to use an air cleaner is left to the individual.
Will Using This Method Reduce Health Effects?
This method may reduce the health effects from some
particles - small solid or liquid substances suspended in air, such as dust or light spray
Some air cleaners, under the right conditions, can
effectively remove certain respirable-size particles (for example, tobacco smoke
particles). These invisible particles are of concern because they can be inhaled deeply
into the lungs. Removing such particles may reduce associated health effects in exposed
people. These effects may range from eye and lung irritation to more serious effects such
as cancer and decreased lung function.
Some controversy exists about whether air cleaners can
reduce the allergic reactions produced by larger particles such as pollen, house dust
allergens, some molds, and animal dander. Most of these particles are found where they
settle on surfaces in the home, rather than in the air. They cannot be removed by an air
cleaner unless disturbed and re-suspended in the air.
Air cleaners that do not contain special media, such as
activated carbon or alumina, will not remove gaseous pollutants, including radon, or
reduce their associated health effects. Whether air cleaners that contain these media are
effective in reducing health risks from gaseous pollutants cannot be adequately assessed
at this time. In addition, the effectiveness of air cleaners in reducing the health risks
from radon progeny (decay products) cannot be adequately evaluated at present. The removal
of gaseous pollutants and radon and its progeny is not addressed further in this fact
sheet. Health effects from these pollutants may be serious, however, and they are of
concern in indoor air.
Some devices may be installed in the ducts which are part
of central heating or air-conditioning systems in homes. Portable units stand alone in a
Types of air cleaners include:
- Mechanical filters, similar to, and including, the typical
- Electronic air cleaners (for example, electrostatic
precipitators) which trap charged particles using an electrical field.
- Ion generators which act by charging the particles in a
room. The charged particles are then attracted to walls, floors, draperies, etc. or a
- "Hybrid" devices, which contain two or more of the
particle removal devices discussed above.
Assessing Potential Performance
At a minimum, you should consider the following major
factors affecting the performance of the air cleaner:
- The percentage of the particles removed as they go through
the device (that is, the efficiency).
- The amount of air handled by the device. For example, an air
cleaner may have a high efficiency filter, but it may process only 10 cubic feet of air
each minute. Suppose that the air cleaner is put in a room of typical size, containing
1000 cubic feet of air. In this room, it will take a long time for all the air to be
processed. In some cases, pollutants may be generated more quickly than they are removed.
- The effective volume of the air to be cleaned. A single
portable unit used in a room within a large building in which the air flows between
several apartments or offices would be of little or no value.
- The decrease in performance which may occur between
maintenance periods and if periodic maintenance is not performed on schedule.
Additional Factors To Consider
- Ion generators and electronic air cleaners may produce
ozone, particularly if they are not properly installed and maintained or used properly.
Please read your owner's manuals.
- Gases and odors from particles collected by the devices may
be re-dispersed into the air.
- The odor of tobacco smoke is largely due to gases in the
smoke, rather than particles. Thus, you may smell a tobacco odor even when the smoke
particles have been removed.
- Some devices scent the air to mask odors, which may lead you
to believe that the odor-causing pollutants have been removed. However this is not true
for the units sold here.
- Ion generators, especially those that do not contain a
collector, may cause soiling of surfaces. However, this can be cleaned quickly with a
- Maintenance costs, such as costs for the replacement of
filters, may be significant. You should consider these costs in addition to the initial
cost of purchase. In general, the most effective units are also the most costly.
Obtaining Adequate Performance
- Proper installation, use, and care. Follow the
manufacturer's directions to assure that the air cleaner works properly. To avoid any
electrical or mechanical hazards, be sure the unit is listed with Underwriters
Laboratories (UL) or another recognized independent safety testing laboratory.
- Perform routine maintenance, as required. Generally
speaking, air cleaners rigor frequent cleaning and filter replacement to function
- Proper placement. Place portable air cleaners so:
- They are near a specific pollutant source, if one exists.
- They force the cleaned air into occupied areas.
- The inlet and outlet are not blocked by walls, furniture, or other obstructions.
- For in-duct devices, assure that the inlets and outlets of the heating or cooling
system are not blocked by furniture and other obstructions.
One common method of rating high efficiency filters uses a
procedure in Military Standard 282. This procedure measures how well small particles of a
specific chemical are removed by the filter.
The Federal government has not published guidelines or
standards that can be used to determine how well low to medium efficiency this type of
purifiers work. However, standards have been developed by private standard-setting trade
associations. These standards may be useful in comparing air cleaners.