Should You Have the Air
Ducts in Your Home Cleaned?
Most people are now aware that indoor air
pollution is an issue of growing concern and increased visibility.
Many companies are marketing products and services intended to
improve the quality of your indoor air. You have probably seen an
advertisement, received a coupon in the mail, or been approached
directly by a company offering to clean your air ducts as a means
of improving your home's indoor air quality.
These services typically -- but not always --
range in cost from $450 to $1,000 per heating and cooling system,
depending on the services offered, the size of the system to be
cleaned, system accessibility, climatic region, and level of
contamination.
Duct cleaning generally refers to the cleaning
of various heating and cooling system components of forced air
systems, including the supply and return air ducts and registers,
grilles and diffusers, heat exchangers heating and cooling coils,
condensate drain pans (drip pans), fan motor and fan housing, and
the air handling unit housing.
If not properly installed, maintained, and
operated, these components may become contaminated with particles
of dust, pollen or other debris. If moisture is present, the
potential for microbiological growth (e.g., mold) is increased and
spores from such growth may be released into the home's living
space. Some of these contaminants may cause allergic reactions or
other symptoms in people if they are exposed to them.
If you decide to have your heating and cooling
system cleaned, it is important to make sure the service provider
agrees to clean all components of the system and is qualified to
do so. Failure to clean a component of a contaminated system can
result in re-contamination of the entire system, thus negating any
potential benefits. Methods of duct cleaning vary, although
standards have been established by industry associations concerned
with air duct cleaning. Typically, a service provider will use
specialized tools to dislodge dirt and other debris in ducts, then
vacuum them out with a high-powered vacuum cleaner.
In addition, the service provider may propose
applying chemical biocides, designed to kill microbiological
contaminants, to the inside of the duct work and to other system
components. Some service providers may also suggest applying
chemical treatments (sealants or other encapsulants) to seal or
cover the inside surfaces of the air ducts and equipment housings
because they believe the sealant will control mold growth or
prevent the release of dirt particles or fibers from ducts.
These practices have yet to be fully researched
and you should be fully informed before deciding to permit the use
of biocides or sealants in your air ducts. They should only be
applied, if at all, after the system has been properly cleaned of
all visible dust or debris.
Deciding Whether or Not to Have
Your Air Ducts Cleaned
Knowledge about the potential benefits and
possible problems of air duct cleaning is limited. Since
conditions in every home are different, it is impossible to
generalize about whether or not air duct cleaning in your home
would be beneficial.
You may consider having your air ducts cleaned
simply because it seems logical that air ducts will get dirty over
time and should occasionally be cleaned. While the debate about
the value of periodic duct cleaning continues, no evidence
suggests that such cleaning would be detrimental, provided that it
is done properly.
On the other hand, if a service provider fails
to follow proper duct cleaning procedures, duct cleaning can cause
indoor air problems. For example, an inadequate vacuum collection
system can release more dust, dirt, and other contaminants than if
you had left the ducts alone. A careless or inadequately trained
service provider can damage your ducts or heating and cooling
system, possibly increasing your heating and air conditioning
costs or forcing you to undertake difficult and costly repairs or
replacements.
You should consider having the air ducts in your
home cleaned if:
- There is substantial visible mold growth
inside hard surface (e.g., sheet metal) ducts or on other
components of your heating and cooling system. There are
several important points to understand concerning mold
detection in heating and cooling systems:
- Many sections of your heating and cooling
system may not be accessible for a visible inspection, so
ask the service provider to show you any mold they say
exists.
- You should be aware that although a
substance may look like mold , a positive determination of
whether it is mold or not can b e made only by an expert
and may require laboratory analysis for final
confirmation. For about $50, some microbiology
laboratories can tell you whether a sample sent to them on
a clear strip of sticky household tape is mold or simply a
substance that resembles it.
- If you have insulated air ducts and the
insulation gets wet or moldy it cannot be effectively
cleaned and should be removed and replaced.
- If the conditions causing the mold growth
in the first place are not corrected, mold growth will
recur.
- Ducts are infested with vermin, e.g. (rodents
or insects); or
- Ducts are clogged with excessive amounts of
dust and debris and/or particles are actually released into
the home from your supply registers.
Other Important
Considerations...
Duct cleaning has never been shown to actually
prevent health problems. Neither do studies conclusively
demonstrate that particle (e.g., dust) levels in homes increase
because of dirty air ducts or go down after cleaning. This is
because much of the dirt that may accumulate inside air ducts
adheres to duct surfaces and does not necessarily enter the living
space. It is important to keep in mind that dirty air ducts are
only one of many possible sources of particles that are present in
homes.
Pollutants that enter the home both from
outdoors and indoor activities such as cooking, cleaning, smoking,
or just moving around can cause greater exposure to contaminants
than dirty air ducts. Moreover, there is no evidence that a light
amount of household dust or other particulate matter in air ducts
poses any risk to health.
If you think duct cleaning might be a good idea
for your home, but you are not sure, talk to a professional. The
company that services your heating and cooling system may be a
good source of advice. You may also want to contact professional
duct cleaning service providers and ask them about the services
they provide. Remember, they are trying to sell you a service, so
ask questions and insist on complete and knowledgeable answers.
Suggestions for Choosing a Duct
Cleaning Service Provider
- To find companies that provide duct cleaning
services, check your Yellow Pages under "duct
cleaning". Talk to at least three different service
providers and get written estimates before deciding whether to
have your ducts cleaned. When the service providers come to
your home, ask them to show you the contamination that would
justify having your ducts cleaned.
- Do not hire duct cleaners who make sweeping
claims about the health benefits of duct cleaning -- such
claims are unsubstantiated. Do not hire duct cleaners who
recommend duct cleaning as a routine part of your heating and
cooling system maintenance.
- Do not allow the use of chemical biocides or
sealants unless you fully understand the pros and the cons.
- Check references to be sure other customers
were satisfied and did not experience any problems with their
heating and cooling system after cleaning.
- Contact your county or city office of
consumer affairs or local Better Business Bureau to determine
if complaints have been lodged against any of the companies
you are considering.
- Interview potential service providers to
ensure:
- they are experienced in duct cleaning and
have worked on systems like yours;
- they will use procedures to protect you,
your pets, and your home from contamination; and
- they comply with air duct cleaning
standards and, if your ducts are constructed of fiber
glass duct board or insulated internally with fiber glass
duct liner, with the North American Insulation
Manufacturers Association's (NAIMA) recommendations.
- If the service provider charges by the hour,
request an estimate of the number of hours or days the job
will take, and find out whether there will be interruptions in
the work. Make sure the duct cleaner you choose will provide a
written agreement outlining the total cost and scope of the
job before work begins.
What to Expect From an Air Duct
Cleaning Service Provider
If you choose to have your ducts cleaned, the
service provider should:
- Open access ports or doors to allow the
entire system to be cleaned and inspected.
- Inspect the system before cleaning to be sure
that there are no asbestos-containing materials (e.g.,
insulation, register boots, etc.) in the heating and cooling
system. Asbestos-containing materials require specialized
procedures and should not be disturbed or removed except by
specially trained and equipped contractors.
- Use vacuum equipment that exhausts particles
outside of the home or use only high-efficiency particle air (HEPA)
vacuuming equipment if the vacuum exhausts inside the home.
- Protect carpet and household furnishings
during cleaning.
- Use well-controlled brushing of duct surfaces
in conjunction with contact vacuum cleaning to dislodge dust
and other particles.
- Use only soft-bristled brushes for fiberglass
duct board and sheet metal ducts internally lined with
fiberglass. (Although flex duct can also be cleaned using
soft-bristled brushes, it can be more economical to simply
replace accessible flex duct.)
- Take care to protect the duct work, including
sealing and re-insulating any access holes the service
provider may have made or used so they are airtight.
- Follow standards for air duct cleaning and
NAIMA's recommended practice for ducts containing fiber glass
lining or constructed of fiber glass duct board.
How to Determine if the Duct
Cleaner Did A Thorough Job
A thorough visual inspection is the best way to
verify the cleanliness of your heating and cooling system. Some
service providers use remote photography to document conditions
inside ducts. All portions of the system should be visibly clean;
you should not be able to detect any debris with the naked eye.
After completing the job, ask the service provider to show you
each component of your system to verify that the job was performed
satisfactorily.
How to Prevent Duct
Contamination
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.
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.
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.
In the meantime...
Before allowing a service provider to use a
chemical biocide in your duct work, the service provider should:
1. 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.
2. 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:
1. Show you the biocide label, which will
describe its range of approved uses.
2. Apply the biocide only to un-insulated areas
of the duct system after proper cleaning, if necessary to reduce
the chances for re-growth of mold.
3. 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.
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.
Most organizations concerned with duct cleaning,
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 appropriate guidelines or standards. |
