Contents
What Causes Indoor Air Problems?
How Does Outdoor Air Enter a House?
What if You Live in an Apartment?
Indoor pollution sources that release
gases or particles into the air are the primary cause of indoor air
quality problems in homes. Inadequate ventilation can increase
indoor pollutant levels by not bringing in enough outdoor air to
dilute emissions from indoor sources and by not carrying indoor air
pollutants out of the home. High temperature and humidity levels can
also increase concentrations of some pollutants.
Pollutant Sources
There are many sources of indoor
air pollution in any home. These include combustion sources such
as oil, gas, kerosene, coal, wood, and tobacco products; building
materials and furnishings as diverse as deteriorated,
asbestos-containing insulation, wet or damp carpet, and cabinetry
or furniture made of certain pressed wood products; products for
household cleaning and maintenance, personal care, or hobbies;
central heating and cooling systems and humidification devices;
and outdoor sources such as radon,
pesticides, and outdoor air pollution.
The relative importance of any
single source depends on how much of a given pollutant it emits
and how hazardous those emissions are. In some cases, factors such
as how old the source is and whether it is properly maintained are
significant. For example, an improperly adjusted gas stove can
emit significantly more carbon monoxide than one that is properly
adjusted.
Some sources, such as building
materials, furnishings, and household products like air
fresheners, release pollutants more or less continuously. Other
sources, related to activities carried out in the home, release
pollutants intermittently. These include smoking, the use of
unvented or malfunctioning stoves, furnaces, or space heaters, the
use of solvents in cleaning and hobby activities, the use of paint
strippers in redecorating activities, and the use of cleaning
products and pesticides in housekeeping. High pollutant
concentrations can remain in the air for long periods after some
of these activities.
Amount of Ventilation
If too little outdoor air enters a
home, pollutants can accumulate to levels that can pose health and
comfort problems. Unless they are built with special mechanical
means of ventilation, homes that are designed and constructed to
minimize the amount of outdoor air that can "leak" into and out of
the home may have higher pollutant levels than other homes.
However, because some weather conditions can drastically reduce
the amount of outdoor air that enters a home, pollutants can build
up even in homes that are normally considered "leaky."
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Outdoor air enters and leaves a house
by: infiltration, natural ventilation, and mechanical ventilation.
In a process known as infiltration, outdoor air flows into the house
through openings, joints, and cracks in walls, floors, and ceilings,
and around windows and doors. In natural ventilation, air moves
through opened windows and doors. Air movement associated with
infiltration and natural ventilation is caused by air temperature
differences between indoors and outdoors and by wind. Finally, there
are a number of mechanical ventilation devices, from outdoor-vented
fans that intermittently remove air from a single room, such as
bathrooms and kitchen, to air handling systems that use fans and
duct work to continuously remove indoor air and distribute filtered
and conditioned outdoor air to strategic points throughout the
house. The rate at which outdoor air replaces indoor air is
described as the air exchange rate. When there is little
infiltration, natural ventilation, or mechanical ventilation, the
air exchange rate is low and pollutant levels can increase.
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Apartments can have the same indoor
air problems as single-family homes because many of the pollution
sources, such as the interior building materials, furnishings, and
household products, are similar. Indoor air problems similar to
those in offices are caused by such sources as contaminated
ventilation systems, improperly placed outdoor air intakes, or
maintenance activities.
Solutions to air quality problems in
apartments, as in homes and offices, involve such actions as:
eliminating or controlling the sources of pollution, increasing
ventilation, and installing air cleaning devices. Often a resident
can take the appropriate action to improve the indoor air quality by
removing a source, altering an activity, unblocking an air supply
vent, or opening a window to temporarily increase the ventilation;
in other cases, however, only the building owner or manager is in a
position to remedy the problem.
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