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Indoor Air Pollution
Improving Indoor Air Quality
The information provided here is
based on current scientific and technical understanding of the issues
presented.
Following
the advice given will not necessarily provide complete protection in all
situations or against all health hazards that may be caused by indoor air
pollution.
There are three basic strategies to improve indoor air
quality
1. Source Control
2. Improved Ventilation
3. Air Cleaners
Source Control
Usually the most effective way to improve indoor air
quality is to eliminate individual sources of pollution or to reduce their
emissions.
Some sources, like those that
contain asbestos, can be sealed or enclosed; others, like gas stoves, can be
adjusted to decrease the amount of emissions.
In
many cases, source control is also a more cost-efficient approach to protecting
indoor air quality than increasing ventilation because increasing ventilation
can increase energy costs.
Ventilation Improvements
For most indoor air quality problems in the home,
source control is the most effective solution.
Another approach to lowering the concentrations of
indoor air pollutants in your home is to increase the amount of outdoor air
coming indoors.
Most home heating and cooling
systems, including forced air heating systems, do not mechanically bring fresh
air into the house.
Opening
windows and doors, operating window or attic fans, when the weather permits, or
running a window air conditioner with the vent control open increases the
outdoor ventilation rate.
Local
bathroom or kitchen fans that exhaust outdoors remove contaminants directly
from the room where the fan is located and also increase the outdoor air
ventilation rate.
It is particularly important to
take as many of these steps as possible while you are involved in short-term
activities that can generate high levels of pollutants — for example, painting,
paint stripping, heating with kerosene heaters, cooking, or engaging in
maintenance and hobby activities such as welding, soldering, or sanding.
You
might also choose to do some of these activities outdoors, if you can and if
weather permits.
Advanced designs of new homes are
starting to feature mechanical systems that bring outdoor air into the home.
Some of these designs include energy-efficient heat recovery ventilators (also
known as air-to-air heat exchangers).
Ventilation
and shading can help control indoor temperatures.
Ventilation
also helps remove or dilute indoor airborne pollutants coming from indoor
sources. This reduces the level of contaminants and improves indoor air quality
(IAQ).
Carefully
evaluate using ventilation to reduce indoor air pollutants where there may be
outdoor sources of pollutants, such as smoke or refuse, nearby.
The introduction of outdoor air
is one important factor in promoting good air quality. Air may enter a home in
several different ways, including:
· through
natural ventilation, such as through windows and doors
· through
mechanical means, such as through outdoor air intakes associated with the
heating, ventilation and air conditioning (HVAC) system
· through
infiltration, a process by which outdoor air flows into the house through
openings, joints and cracks in walls, floors and ceilings, and around
windows and doors.
Infiltration occurs in all homes
to some extent.
Natural ventilation describes air
movement through open windows and doors.
If
used properly natural ventilation can at times help moderate the indoor air
temperature, which may become too hot in homes without air-conditioning systems
or when power outages or brownouts limit or make the use of air conditioning
impossible.
Natural ventilation can also
improve indoor air quality by reducing pollutants that are indoors. Examples of
natural ventilation are:
· opening
windows and doors
· window
shading such as closing the blinds
Most residential forced
air-heating systems and air-conditioning systems do not bring outdoor air into
the house mechanically, and infiltration and natural ventilation are relied
upon to bring outdoor air into the home.
Advanced
designs for new homes are starting to add a mechanical feature that brings
outdoor air into the home through the HVAC system.
Some
of these designs include energy efficient heat recovery ventilators to mitigate
the cost of cooling and heating this air during the summer and winter.
Air Cleaners
There are many types and sizes of
air cleaners on the market, ranging from relatively inexpensive table-top
models to sophisticated and expensive whole-house systems.
Some
air cleaners are highly effective at particle removal, while others, including
most table-top models, are much less so.
Air
cleaners are generally not designed to remove gaseous pollutants.
The
effectiveness of an air cleaner depends on how well it collects pollutants from
indoor air (expressed as a percentage efficiency rate) and how much air it
draws through the cleaning or filtering element (expressed in cubic feet per
minute).
A very efficient collector with a
low air-circulation rate will not be effective, nor will a cleaner with a high
air-circulation rate but a less efficient collector.
The
long-term performance of any air cleaner depends on maintaining it according to
the manufacturer's directions.
Another important factor in
determining the effectiveness of an air cleaner is the strength of the
pollutant source.
Table-top
air cleaners, in particular, may not remove satisfactory amounts of pollutants
from strong nearby sources.
People
with a sensitivity to particular sources may find that air cleaners are helpful
only in conjunction with concerted efforts to remove the source.
Over the past few years, there
has been some publicity suggesting that houseplants have been shown to reduce
levels of some chemicals in laboratory experiments.
There
is currently no evidence, however, that a reasonable number of houseplants
remove significant quantities of pollutants in homes and offices.
Indoor
houseplants should not be over-watered because overly damp soil may promote the
growth of microorganisms which can affect allergic individuals.
At present, EPA does not
recommend using air cleaners to reduce levels of radon and its decay products.
The
effectiveness of these devices is uncertain because they only partially remove
the radon decay products and do not diminish the amount of radon entering the
home.
EPA
plans to do additional research on whether air cleaners are, or could become, a
reliable means of reducing the health risk from radon.
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