Whether
or not you decide to have the air ducts in your home cleaned,
committing to a good preventive maintenance program is essential to
minimize duct contamination.
To prevent dirt from entering the system:
Use the highest efficiency air filter
recommended by the manufacturer of your heating and cooling
system.
Change filters regularly.
If your filters become clogged, change
them more frequently.
Be sure you do not have any missing
filters and that air cannot bypass filters through gaps around the
filter holder.
When having your heating and cooling
system maintained or checked for other reasons, be sure to ask the
service provider to clean cooling coils and drain pans.
During construction or renovation work
that produces dust in your home, seal off supply and return
registers and do not operate the heating and cooling system until
after cleaning up the dust.
Remove dust and vacuum your home
regularly. (Use a high efficiency vacuum (HEPA) cleaner or the
highest efficiency filter bags your vacuum cleaner can take.
Vacuuming can increase the amount of dust in the air during and
after vacuuming as well as in your ducts).
If your heating system includes in-duct
humidification equipment, be sure to operate and maintain the
humidifier strictly as recommended by the manufacturer.
To prevent ducts from becoming wet:
Moisture should not be present in ducts.
Controlling moisture is the most effective way to prevent biological
growth in air ducts.
Moisture can enter the duct system through
leaks or if the system has been improperly installed or serviced.
Research suggests that condensation (which occurs when a surface
temperature is lower than the dew point temperature of the
surrounding air) on or near cooling coils of air conditioning units
is a major factor in moisture contamination of the system. The
presence of condensation or high relative humidity is an important
indicator of the potential for mold growth on any type of duct.
Controlling moisture can often be difficult, but here are some steps
you can take:
Promptly and properly repair any leaks
or water damage.
Pay particular attention to cooling
coils, which are designed to remove water from the air and can be
a major source of moisture contamination of the system that can
lead to mold growth. Make sure the condensate pan drains properly.
The presence of substantial standing water and/or debris indicates
a problem requiring immediate attention. Check any insulation near
cooling coils for wet spots.
Make sure ducts are properly sealed and
insulated in all non-air-conditioned spaces (e.g., attics and
crawl spaces). This will help to
prevent moisture due to condensation from entering the system and
is important to make the system work as intended. To prevent water
condensation, the heating and cooling system must be properly
insulated.
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Table of Contents
Does duct cleaning
prevent health problems?
The
bottom line is: no one knows. There are examples of ducts that have
become badly contaminated with a variety of materials that may pose
risks to your health. The duct system can serve as a means to
distribute these contaminants throughout a home. In these cases,
duct cleaning may make sense. However, a light amount of household
dust in your air ducts is normal. Duct cleaning is not considered to
be a necessary part of yearly maintenance of your heating and
cooling system, which consists of regular cleaning of drain pans and
heating and cooling coils, regular filter changes and yearly
inspections of heating equipment. Research continues in an effort to
evaluate the potential benefits of air duct cleaning.
In the meantime...
Educate yourself about duct cleaning by
contacting some or all of the sources of information listed at the
end of this publication and asking questions of potential service
providers.
Are
duct materials other than bare sheet metal ducts more likely to be
contaminated with mold and other biological contaminants?
You
may be familiar with air ducts that are constructed of sheet metal.
However, many modern residential air duct systems are constructed of
fiber glass duct board or sheet metal ducts that are lined on the
inside with fiber glass duct liner. Since the early 1970's, a
significant increase in the use of flexible duct, which generally is
internally lined with plastic or some other type of material, has
occurred. The use of insulated duct material has increased due to
improved temperature control, energy conservation, and reduced
condensation. Internal insulation provides better acoustical (noise)
control. Flexible duct is very low cost. These products are
engineered specifically for use in ducts or as ducts themselves, and
are tested in accordance with standards established by Underwriters
Laboratories (UL), the American Society for Testing and Materials
(ASTM), and the National Fire Protection Association (NFPA).
Many insulated duct systems have operated for
years without supporting significant mold growth. Keeping them
reasonably clean and dry is generally adequate. However, there is
substantial debate about whether porous insulation materials (e.g.,
fiber glass) are more prone to microbial contamination than bare
sheet metal ducts. If enough dirt and moisture are permitted to
enter the duct system, there may be no significant difference in the
rate or extent of microbial growth in internally lined or bare sheet
metal ducts. However, treatment of mold contamination on bare sheet
metal is much easier. Cleaning and treatment with an EPA-registered
biocide are possible. Once fiberglass duct liner is contaminated
with mold, cleaning is not sufficient to prevent regrowth and there
are no EPA-registered biocides for the treatment of porous duct
materials. EPA, NADCA, and NAIMA
all recommend the replacement of wet or moldy fiber glass duct
material.
In the meantime...
- Experts do agree that moisture should
not be present in ducts and if moisture and dirt are present, the
potential exists for biological contaminants to grow and be
distributed throughout the home. Controlling moisture is the most
effective way to prevent biological growth in all types of air
ducts.
- Correct any water leaks or standing
water.
- Remove standing water under cooling
coils of air handling units by making sure that drain pans slope
toward the drain.
- If humidifiers are used, they must be
properly maintained.
- Air handling units should be constructed
so that maintenance personnel have easy, direct access to heat
exchange components and drain pans for proper cleaning and
maintenance.
- Fiber glass, or any other insulation
material that is wet or visibly moldy (or if an unacceptable odor
is present) should be removed and replaced by a qualified heating
and cooling system contractor.
- Steam cleaning and other methods
involving moisture should not be used on any kind of duct work.
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Table of Contents
Should chemical
biocides be applied to the inside of air ducts?
Air
duct cleaning service providers may tell you that they need to apply
a chemical biocide to the inside of your ducts to kill bacteria
(germs), and fungi (mold) and prevent future biological growth. Some
duct cleaning service providers may propose to introduce ozone to
kill biological contaminants. Ozone is a highly reactive gas that is
regulated in the outside air as a lung irritant. However, there
remains considerable controversy over the necessity and wisdom of
introducing chemical biocides or ozone into the duct work.
Among the possible problems with biocide and
ozone application in air ducts:
- Little research has been conducted to
demonstrate the effectiveness of most biocides and ozone when used
inside ducts. Simply spraying or otherwise introducing these
materials into the operating duct system may cause much of the
material to be transported through the system and released into
other areas of your home.
- Some people may react negatively to the
biocide or ozone, causing adverse health reactions.
Chemical biocides are regulated by EPA under
Federal pesticide law. A product must be registered by EPA for a
specific use before it can be legally used for that purpose. The
specific use(s) must appear on the pesticide (e.g., biocide) label,
along with other important information. It is a violation of federal
law to use a pesticide product in any manner inconsistent with the
label directions.
A small number of products are currently
registered by EPA specifically for use on the inside of bare sheet
metal air ducts. A number of products are also registered for use as
sanitizers on hard surfaces, which could include the interior of
bare sheet metal ducts. While many such products may be used legally
inside of unlined ducts if all label directions are followed, some
of the directions on the label may be inappropriate for use in
ducts. For example, if the directions indicate "rinse with
water", the added moisture could stimulate mold growth.
All of the products discussed above are
registered solely for the purpose of sanitizing the smooth surfaces
of unlined (bare) sheet metal ducts. No products are currently
registered as biocides for use on fiber glass duct board or fiber
glass lined ducts, so it is important to determine if sections of
your system contain these materials before permitting the
application of any biocide.
In the meantime...
Before allowing a service provider to use a
chemical biocide in your duct work, the service provider should:
Demonstrate visible evidence of
microbial growth in your duct work.
Some service providers may attempt to convince you that your air
ducts are contaminated by demonstrating that the microorganisms
found in your home grow on a settling plate (i.e., petri dish).
This is inappropriate. Some microorganisms are always present in
the air, and some growth on a settling plate is normal. As noted
earlier, only an expert can positively identify a substance as
biological growth and lab analysis may be required for final
confirmation. Other testing methods are not reliable.
Explain why biological growth cannot be
removed by physical means, such as brushing, and further growth
prevented by controlling moisture.
If you decide to permit the use of a biocide,
the service provider should:
Show you the biocide label, which will
describe its range of approved uses.
Apply the biocide only to un-insulated
areas of the duct system after proper cleaning, if necessary to
reduce the chances for regrowth of mold.
Always use the product strictly
according to its label instructions.
While some low toxicity products may be
legally applied while occupants of the home are present, you may
wish to consider leaving the premises while the biocide is being
applied as an added precaution.
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Table of Contents
Do sealants prevent
the release of dust and dirt particles into the air?
Manufacturers
of products marketed to coat and seal duct surfaces claim that these
sealants prevent dust and dirt particles inside air ducts from being
released into the air. As with biocides, a sealant is often applied
by spraying it into the operating duct system. Laboratory tests
indicate that materials introduced in this manner tend not to
completely coat the duct surface. Application of sealants may also
affect the acoustical (noise) and fire retarding characteristics of
fiber glass lined or constructed ducts and may invalidate the
manufacturer's warranty.
Questions about the safety, effectiveness and
overall desirability of sealants remain. For example, little is
known about the potential toxicity of these products under typical
use conditions or in the event they catch fire.
In addition, sealants have yet to be evaluated
for their resistance to deterioration over time which could add
particles to the duct air.
In the meantime...
Most organizations concerned with duct
cleaning, including EPA, NADCA,
NAIMA, and the Sheet Metal and Air
Conditioning Contractors' National Association (SMACNA) do not
currently recommend the routine use of sealants in any type of duct.
Instances when the use of sealants may be appropriate include the
repair of damaged fiber glass insulation or when combating fire
damage within ducts. Sealants should never be used on wet duct
liner, to cover actively growing mold, or to cover debris in the
ducts, and should only be applied after cleaning according to
NADCA or other appropriate guidelines or
standards.
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Table of Contents
U.S.
Environmental Protection Agency
Office
of Radiation and Indoor Air
Indoor Environments Division
(6604J)
401 M St., S.W.
Washington, DC 20460
(202)
564-9370
(202) 565-2038 (fax)
E-mail:
webmaster.oria@epamail.epa.gov
World Wide Web
Site:
http://www.epa.gov/iaq/
Indoor Air
Quality Information
Clearinghouse (IAQ INFO)
P.O. Box 37133
Washington, DC
20013-7133
1 (800) 438-4318
(202) 484-1307
E-mail: IAQINFO@aol.com
Useful EPA publications available free of
charge from either location above:
Consumer Research Council (CRC)
IAQ Checklist
P.O. Box 12099
Washington, DC
20005-0999
Ask for: How
Healthy Is The Air In Your Home?
(Free. Send a self-addressed, stamped standard size business
envelope)
To Learn More About
Air Duct
Cleaning
National Air Duct
Cleaners
Association (NADCA)
1518 K Street, NW Suite 503
Washington, DC 20005
(202) 737-2926
http://www.nadca.com
Ask for:
Introduction to HVAC (Heating, Ventilating, and Air Conditioning)
System Cleaning Services
(Although intended for commercial customers, information can be
useful to consumers.)
North American
Insulation Manufacturers
Association (NAIMA)
44 Canal Center Plaza, Suite 310
Alexandria, VA 22314
(703) 684-0084
Ask for: Cleaning
Fibrous Glass Insulated Air Duct Systems; Recommended Practice
Other Useful
Resources
For a free list of state and local consumer
protection agencies and Better Business Bureaus:
Consumer's Resource Handbook
Consumer Information Center
Pueblo, CO 81009
For Information on Antimicrobial Biocides:
National Antimicrobial Information
Network (NAIN)
1 (800) 447-6349.
Email: nain@ace.orst.edu
Go back to the
Table of Contents
 |
Learn as much as possible about air duct
cleaning before you decide to have your ducts cleaned by reading
this guidance and contacting the sources of information
provided. |
|
|
Consider other possible sources of indoor air pollution first
if you suspect an indoor air quality problem exists in your
home. |
|
|
Have your air ducts cleaned if they are
visibly contaminated with substantial mold growth, pests or
vermin, or are clogged with substantial deposits of dust or
debris. |
|
|
Ask the service provider to show you any
mold or other biological contamination they say exists. Get
laboratory confirmation of mold growth or decide to rely on your
own judgement and common sense in evaluating apparent mold
growth. |
|
|
Get estimates from at least three service
providers. |
|
|
Check references. |
|
|
Ask the service provider whether he/she
holds any relevant state licenses. As of 1996, the following
states require air duct cleaners to hold special licenses:
Arizona, Arkansas, California, Florida, Georgia, Michigan and
Texas. Other states may also require licenses. |
|
|
Insist that the service provider give you
knowledgeable and complete answers to your questions.
|
|
|
Find out whether your ducts are made of
sheet metal, flex duct, or constructed of fiber glass duct board
or lined with fiber glass since the methods of cleaning vary
depending on duct type. Remember, a combination of these
elements may be present. |
|
|
Permit the application of biocides in your
ducts only if necessary to control mold growth and only after
assuring yourself that the product will be applied strictly
according to label directions. As a precaution, you and your
pets should leave the premises during application.
|
|
|
Do not permit the use of sealants except
under unusual circumstances where other alternatives are not
feasible. |
|
|
Make sure the service provider follows the
National Air Duct Cleaning Association's
(NADCA) standards and, if the ducts are constructed of
flex duct, duct board, or lined with fiber glass, the guidelines
of the North American Insulation Manufacturers
Association (NAIMA). |
|
|
Commit to a preventive maintenance program
of yearly inspections of your heating and cooling system,
regular filter changes, and steps to prevent moisture
contamination. |
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Table of Contents
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