Should You Have the Air Ducts in Your Home Cleaned?
Part 1 of 2
Note: This article was authored and researched by the US
Environmental Protection Agency. It is a thorough, honest
treatment of a home repair procedure fraught with deception and
outright fraud by unscrupulous contractors. Do
your homework and READ this important article before you invest
in duct cleaning. NH
What is Air Duct Cleaning?
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
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 (see diagram below.)
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
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. [Click on the graphic below for a full page "printable"
Components of a
Residential Heating and
Upright Indoor System
(e.g., heat pump, gas, electric), size, position
of system components will vary.
Deciding Whether or Not to Have
Your Air Ducts Cleaned
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.
If no one in your household suffers from
allergies or unexplained symptoms or illnesses and if, after a
visual inspection of the inside of the ducts, you see no indication
that your air ducts are contaminated with large deposits of dust or
mold (no musty odor or visible mold growth), having your air ducts
cleaned is probably unnecessary. It is normal for the return
registers to get dusty as dust-laden air is pulled through the
grate. This does not indicate that your air ducts are contaminated
with heavy deposits of dust or debris; the registers can be easily
vacuumed or removed and cleaned.
On the other hand, if family members are
experiencing unusual or unexplained symptoms or illnesses that you
think might be related to your home environment, you should discuss
the situation with your doctor. EPA has published Indoor
Air Quality: An Introduction for Health Professionals
that can be obtained free of charge by contacting IAQ
INFO at the number listed in this
guide. You may obtain another free EPA booklet from IAQ INFO
Inside Story: A Guide to Indoor Air Quality
for guidance on identifying possible indoor air quality problems and
ways to prevent or fix them.
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
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 be 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.
EPA does not recommend that air ducts be cleaned except on an as-needed
basis because of the continuing uncertainty about the benefits of
duct cleaning under most circumstances.
If a service provider or advertiser asserts that EPA recommends
routine duct cleaning or makes claims about its health benefits, you
should notify EPA by writing to the address listed at the end of
this guidance. EPA does, however, recommend that if you have a fuel
burning furnace, stove, or fireplace, they be inspected for proper
functioning and serviced before each heating season to protect
against carbon monoxide poisoning. Some research also suggests that
cleaning dirty cooling coils, fans and heat exchangers can improve
the efficiency of heating and cooling systems. However, little
evidence exists to indicate that simply cleaning the duct system
will increase your system's efficiency.
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
find companies that provide duct cleaning services, check your
Yellow Pages under "duct cleaning" or contact the
National Air Duct Cleaners Association (NADCA)
at the address and phone number in the information section located
at the end of this guidance. Do not assume that all duct cleaning
service providers are equally knowledgeable and responsible. 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. You should
also be wary of duct cleaners who claim to be certified by EPA. EPA neither establishes duct
cleaning standards nor certifies, endorses, or approves duct
Do not allow the use of chemical
biocides or sealants unless you fully understand the pros and the
cons (See "Unresolved
Issues of Duct Cleaning" in Part 2 of this article).
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
Interview potential service providers
- 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)
Ask the service provider whether they
hold 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 require them as well.
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
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
materials require specialized procedures and should not be
disturbed or removed except by specially trained and equipped
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
Protect carpet and household furnishings
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.
standards for air duct cleaning and
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
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. Show the Post-Cleaning
Consumer Checklist to the service provider before the work
begins. After completing the job, ask the service provider to show
you each component of your system to verify that the job was
If you answer "No" to any of the
questions on the checklist, this may indicate a problem with the
job. Ask your service provider to correct any deficiencies until you
can answer "yes" to all the questions on the checklist.
||Did the service provider obtain access to
and clean the entire heating and cooling system, including
ductwork and all components (drain pans, humidifiers, coils, and
|Has the service provider adequately
demonstrated that duct work and plenums are clean? (Plenum
is a space in which supply or return air is mixed or moves; can be
duct, joist space, attic and crawl spaces, or wall cavity.)
||Is the heat exchanger surface visibly
|Are both sides of the cooling coil
|If you point a flashlight into the
cooling coil, does light shine through the other side? It should
if the coil is clean.
|Are the coil fins straight and evenly
spaced (as opposed to being bent over and smashed together)?
|Is the coil drain pan completely clean
and draining properly?
||Are the blower blades clean and free of
oil and debris?
|Is the blower compartment free of visible
dust or debris?
|Is the return air plenum
free of visible dust or debris?
|Do filters fit properly and
are they the proper efficiency as recommended by HVAC system
|Is the supply air plenum (directly
downstream of the air handling unit) free of moisture stains and
||Are interior ductwork surfaces free of
visible debris? (Select several sites at random in both the return
and supply sides of the system.)
||Is all fiber glass material in good
condition (i.e., free of tears and abrasions; well adhered to
|Are newly installed access doors in sheet
metal ducts attached with more than just duct tape (e.g., screws,
rivets, mastic, etc.)?
|With the system running, is air leakage
through access doors or
very slight or non-existent?
||Have all registers, grilles, and
diffusers been firmly reattached to the walls, floors, and/or
|Are the registers, grilles, and diffusers
|Does the system function properly in both
the heating and cooling modes after cleaning?
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