United Stales
Environmental Protection
Agency
Indoor Environments
Dnision iM.n<)i
Office of Air and Radiation
EPA 402-K-97-002
October 1997
Should You  Have the Air
Ducts In Your Home
Cleaned?

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           Should You Have the Air Ducts in Your Home Cleaned?
                                        Summary
    Knowledge about air duct cleaning is
    in its early stages, so a blanket recom-
mendation cannot be offered as to whether
you should have the air ducts in your home
cleaned.  The U.S.
Environmental  Protection Agency (EPA)
urges you to read  this document in its entirety
as it provides important information on the
subject.

    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. This is
because much of the dirt in 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 your health.
Y
Fou should consider having the air
ducts in your home cleaned if:
V  There is substantial visible mold growth
is present in 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 duct 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 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 substance sent to
       them on a clear strip of sticky house-
       hold  tape is mold or just something
       that resembles it.

*      If you have insulated air ducts and the
       insulation gets wet or moldy it should
       be removed and replaced as it cannot
       be effectively cleaned.

*      If the conditions causing the mold
       growth  in the first place are not cor-
       rected,  mold growth will recur.

V Ducts are infested with vermin (e.g.,
rodents or insects); or

V Ducts are clogged with excessive
amounts of dust and debris and/or par-
ticles are actually released into the home
from your supply registers.

If any of the conditions identified above exists, it
usually suggests one or more underlying causes.
Prior to any cleaning, retrofitting, or replacing of
your ducts, the cause or causes must be corrected
or else the problem will likely recur.

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    Some research suggests that clean-
    ing  heating and cooling system compo-
nents (e.g., cooling coils, fans and heat
exchangers) may improve the efficiency of
your system, resulting in a  longer operating
life, as well as some energy and maintenance
cost savings.  However, little evidence exists
that cleaning only the ducts will improve the
efficiency of the system.

    You may consider having your air
    ducts cleaned simply because it seems
logical that  air ducts will get dirty over time
and should be occasionally cleaned. Pro-
vided that the cleaning is done properly, no
evidence suggests  that  such cleaning would
be detrimental.  EPA does  not recommend
that the  air  ducts be cleaned routinely, but
only as needed. If a service provider or
advertiser asserts that EPA recommends
routine duct cleaning or makes claims about
its health benefits, you should write EPA  (see
address at the back of this  booklet). 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.

  If you do decide to have your air ducts
  cleaned,  take the same consumer precau-
tions you normally would in assessing the
service provider's competence and reliability.
    Air duct cleaning service providers
    may tell you that they need to apply a
chemical biocide to the inside of your ducts as
a means to kill bacteria (germs) and fungi
(mold) and  prevent future biological growth.
They may also propose the application of a
"sealant" to prevent dust and dirt particles
from being released into  the air or to seal air
leaks. You should fully understand the pros
and cons of permitting application of chemical
biocides or sealants.  While the targeted use
of chemical biocides and sealants may be
appropriate under specific circumstances,
research has not demonstrated their effective-
ness in duct cleaning or their potential ad-
verse health effects.  No chemical biocides
are currently registered by EPA for use in
internally- insulated air duct systems
(See page 13).

      Whether or not you decide to have
      the air ducts in your home cleaned,
preventing water and dirt from entering
the system is the most effective way to
prevent contamination (See page 11).

    Call EPA's IAQINFO at (800) 438-4318
     for more information on  indoor
air quality.

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Table of Contents

Summary	1

What Is Air Duct Cleaning?	4

Deciding Whether or Not to Have Your Air
Ducts Cleaned	6

Suggestions for Choosing a Duct Clean-
ing Service Provider	8

What to Expect of an Air Duct Cleaning
Service Provider	9

How to Determine if the Duct Cleaner Did
a Thorough Job	9

How to Prevent Duct Contamination... 11

Unresolved Issues of Duct
Cleaning	12

To Learn More About Indoor Air Quality
and Air Duct Cleaning	16

Consumer Checklist	17

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What is Air Duct Cleaning?

     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, re-
ceived a coupon in the mail, or been ap-
proached directly by a company offering to
clean your air ducts as a means of improving
your home's indoor air quality. These ser-
vices typically ~ but not always ~ range in
cost from $450 to $1000 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 com-
ponents of forced air systems, including the
supply and return air ducts and registers,
grilles and diffusers, heat exchangers, heat-
ing and cooling coils, condensate drain pans
(drip pans), fan motor and fan housing, and
the air handling unit housing (See diagram,
page 5).

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 com-
ponents of the  system  and is qualified to do
so. Failure to clean a component of a con-
taminated system  can  result in re-contamina-
tion of the entire system, thus negating any
potential benefits.  Methods of duct cleaning
vary, although standards have been estab-
lished 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 compo-
nents. Some service providers may also
suggest applying chemical treatments (seal-
ants or other encapsulants) to seal or cover
the inside surfaces of the air ducts and equip-
ment 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 re-
searched and you should be fully informed
before deciding to permit the use of bio-
cides 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.
  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.

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       Components of a Typical
         Residential Heating and
              Cooling System
    ftm HANDLING
    UNIT HOUSING
                                INS-ULA'I'
                             ;i'i:lllV (."':::: : I	"ll DM]
CQ01INQOCHI9
          Upright Indoor System

               w/gas furnace
            "Type (e.g. heal pump, gas, electric), size, position,
             and location ot system compCMienls will vary
                                        RIOWFR

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Deciding Whether or Not to Have
Your Air Ducts Cleaned

    Knowledge about the potential bene-
    fits 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 ill-
nesses 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 symp-
toms 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 Intro-
duction for Health Professionals that can be
obtained free of charge by contacting
IAQINFO at the number listed in the back of
this booklet. You may obtain another free
EPA booklet from IAQINFO entitled  The
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 collec-
tion 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:

Vine re 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 con-
cerning 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 labora-
       tories 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.

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*      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 cor-
       rected, mold growth will recur.

V Ducts are infested with vermin,
(e.g., rodents or insects); or

V Ducts are clogged with excessive
amounts of dust and debris and/or par-
ticles are actually released into the home
from your supply registers.

Other Important Considerations...

    Duct cleaning has never been shown to
    actually prevent health problems.
Studies have not conclusively demonstrated
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 neces-
sarily 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 uncer-
tainty about the benefits of duct cleaning
under most circumstances.  If a service
provider or advertiser asserts that EPA rec-
ommends routine duct cleaning or makes
claims about its health benefits, you should
notify EPA by writing to the address listed in
the back of this booklet.  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 clean-
ing 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.

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Suggestions for Choosing a Duct
Cleaning Service Provider

   To find companies that provide duct clean
   ing 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 back of this booklet.
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 con-
tamination that would justify having your ducts
cleaned.

V  Do not hire duct cleaners who make
sweeping claims about the health benefits
of duct cleaning -- such claims are unsub-
stantiated. Do not hire duct cleaners who
recommend duct cleaning as a routine part of
your heating and cooling system mainte-
nance. 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 cleaning companies.

V  Do not allow the use of chemical bio-
cides or sealants unless you fully under-
stand the pros and the cons
(See page 13).

V  Check references to be sure other
customers were satisfied and did not
experience any problems with their heat-
ing and cooling system after cleaning.

V  Co ntact yo u r co u nty o r city off i ce of
consumer affairs or local Better Business
Bureau to determine if complaints have
been lodged against any of the companies
you are considering.
V  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 NADCA's air
      duct cleaning standards and, if
      your ducts are constructed of
      fiberglass duct board or insulated
      internally with fiberglass  duct
      liner, with the North American
      Insulation Manufacturers
      Association's (NAIMA)
      recommendations.

V  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, Michi-
gan and  Texas. Other states may require
them as  well.

V  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 whetherthere 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.

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What to Expect of an Air Duct
Cleaning Service  Provider

  If you choose to have your ducts cleaned,
  the service provider should:

V  Open access ports or doors to allow
the entire system to be cleaned and in-
spected.

V  Inspect the system before cleaning to
be sure that there are no asbestos-con-
taining 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.

V  Use vacuum equipment that exhausts
particles outside of the home  or use only
high-efficiency particle air (HEPA) vacu-
uming equipment if the vacuum exhausts
inside the home.

V  Protect carpet and household
furnishings during cleaning.

V  Use well-controlled brushing of duct
surfaces in conjunction with contact
vacuum cleaning to dislodge dust and
other particles.

V  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 economi-
cal to  simply replace accessible  flex duct.)

V  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.
V  Follow NADCA's standards for air duct
cleaning and NAIMA's recommended
practiceforducts containing fiberglass
lining or constructed of fiberglass 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 docu-
ment 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 checklist on the
next page to the service provider before the
work begins. After completing the job, ask
the service provider to  show you each compo-
nent of your system to  verify that the job was
performed satisfactorily.

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.

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POST CLEANING CONSUMER CHECKLIST
General
Heating
Cooling
Components
Blower
Plenums
Metal Ducts
Fiberglass
Access
Doors
Air Vents
System
Operation
Did the service provider obtain access to and clean the entire heating
and cooling system, including duct work and all components (drain
pans, humidifiers, coils, and fans)?
Has the service provider adequately demonstrated that duct work and
plenums are Clean? (Plenum is a space in which supply or return air is mixecf or moves;
can be duct, joist space, attic and crawl spaces, or wail cavity.)
'
Is the heat exchanger surface visibly clean?
Are both sides of the cooling coil visibly clean?
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 and debris?
Is the return air plenum free of visible dust and debris?
Do filters fit properly and are they the proper efficiency
as recommended by HVAC system manufacturer?
Is the supply air plenum (directly downstream of the air handling unit)
free of moisture stains and contaminants?
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 fiberglass material in good condition (i.e., free of tears and
abrasions; well adhered to underlying materials)?
Are newly installed access doors in sheet metal ducts attached with
more than just duct tape (e.g., screws, rivets, mastic)?
With the system running, is air leakage through access doors or
covers very slight or non-existent?
Have all registers, grilles, and diffusers been firmly reattached to the
walls, floors, and/or ceilings?
Are the registers, grilles, and diffusers visibly clean?
Does the system function properly in both the heating and cooling
modes after cleaning?
YES



















NO



















10

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How to Prevent Duct
Contamination

     Whether or not you decide to have the air
     ducts in your home cleaned, following a
good preventive maintenance program is
essential to minimize duct contamination.

To prevent dirt from entering the system:

V  Use the highest efficiency airfilter
recommended by the manufacturer of your
heating and cooling system.

V  Change filters regularly.

V  If your filters become clogged, change
them more frequently.

V  Be sure you do not have any missing
filters and that air cannot bypass filters
through gaps around the filter holder.

V  When having your heating and cooling
system maintained or checked for other
reasons, be sure to ask the service pro-
viderto clean cooling coils and drain
pans.

V  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.

V  Remove dust and vacuum your home
regularly. (Use a high efficiency vacuum
(HEPA) cleaner orthe highest efficiency
filter bags your vacuum cleaner can take.
Vacuuming can increase the amount of
dust in the air during and aftervacuuming
as well as in your ducts).

V  If your heating system includes in-duct
humidification equipment, be sure to
operate and maintain the humidifier
strictly as recommended by the manufac-
turer.
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:

V  Promptly and properly repair any leaks
or water damage.

V  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 requir-
ing immediate attention. Check any insula-
tion near cooling coils for wet spots.

V  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 in-
tended. To prevent water condensation, the
heating and  cooling system must be properly
insulated.
                                         11

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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.
   V  If you are replacing your air condition-
   ing system, make sure that the unit is the
   proper size for your needs and that all
   ducts are sealed at the joints. A unit that is
   too big will cycle on and off frequently, result-
   ing in poor moisture removal, particularly in
   areas with high humidity.  Also make sure that
   your new system is designed to manage
   condensation effectively.

   Unresolved Issues of Duct Clean-
   ing

   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...

V  Educate yourself about duct cleaning
by contacting some or all of the sources of
information listed at the end of this publi-
cation 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 fiberglass  duct board or sheet
metal ducts that are lined on the inside with
fiberglass 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 in-
creased due to improved temperature control,
energy conservation, and reduced condensa-
tion. Internal  insulation provides better acous-
tical (noise) control.  Flexible duct is very low
cost.  These products are engineered specifi-
cally 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 insu-
lated duct systems have operated for years
without supporting significant mold growth.
Keeping them reasonably clean and dry is
generally adequate.  However, there is sub-
stantial debate about whether porous insula-
tion materials (e.g., fiberglass) are more
prone to microbial contamination  than bare
sheet metal ducts.  If enough dirt and mois-
ture 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,
                                              12

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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 con-
taminated 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 fiberglass  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.

V  Correct any water leaks or standing
water.

V   Remove standing water under cooling
coils of air handling units by  making sure
that drain pans slope toward the drain.

V   If humidifiers are used, they must be
properly maintained.

V   Airhandlingunitsshouldbecon-
structed so that maintenance personnel
have easy, direct access to heat exchange
components and drain pans for proper
cleaning and maintenance.

V   Fiberglass, 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.

V   Steam cleaning and other methods
involving moisture should not be used on
any kind of duct work.
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 pre-
vent future biological growth. Some duct
cleaning service providers may propose  to
introduce ozone to kill biological contami-
nants.  Ozone is a highly reactive gas that is
regulated in the outside air as a lung irritant.
However, there remains considerable contro-
versy 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 impor-
tant information.  It is a violation of federal law
to use a pesticide product  in any manner
inconsistent with its label directions.

A small number of products are currently
registered by EPA specifically for use on the
inside of bare sheet metal air ducts.
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   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 fiberglass
   duct board or fiberglass lined ducts, so it is
   important to determine if sections of your
   system contain these materials before permit-
   ting the application  of any biocide.
 No products are currently registered by EPA
as biocides for use on fiberglass ductboard or
  fiberglass 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:

   V  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 inap-
   propriate.  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.

V  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:

V  Show you the biocide label, which will
describe its range of approved uses.

V  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 following
cleaning.

V  Always use the product strictly ac-
cording 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 ap-
plied as an added precaution.

Do sealants prevent the release of dust
and dirt particles into the air?
M:
     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 materi-
als 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
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fiberglass 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  poten-
tial 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 fiberglass
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 accord-
ing to NADCA or other appropriate guidelines
or standards.
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To Learn More About Indoor Air
Quality

U.S. Environmental Protection Agency

World Wide Web Site:
http://www.epa.gov/iaq/

Indoor Air Quality Information Clearing-
house (IAQINFO)
P.O. Box37133
Washington, DC 20013-7133
(800)438-4318
FAX:  (703)356-5386

Useful EPA publications available free of
charge from either location above:

*     The Inside Story: A Guide to Indoor
      Air Quality (EPA 404-K-93-007)

*     Indoor Air Pollution: An Introduc-
      tion for Health Professionals
      (EPA402-R-94-007)

*     Residential Air Cleaning Devices: A
      Summary of Available Information
      (EPA 4001-90-002)

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 custom-
ers, 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 Net-
work (NAIN)
(800)447-6349.
Email: nain@ace.orst.edu
                                        16

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Consumer  Checklist

V   Consider other possible sources of indoor
air pollution first if you suspect an indoor air
quality problem exists in your home

V   Learn as much as possible about air duct
cleaning by reading this booklet and contact-
ing the sources of information provided before
you decide to have your ducts cleaned.

V   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.

V   Get estimates from at least three service
providers.

V   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.

V   Find out whether your ducts are made of
sheet metal, flex duct, or constructed  of
fiberglass duct board or lined with fiberglass
since the methods of cleaning vary depending
on duct type.  Remember, a combination of
these elements may be present.

V   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 fiberglass, the guidelines of the North
American Insulation Manufacturers Associa-
tion (NAIMA).

V   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.
V   Insist that the service provider give you
knowledgeable and complete answers to your
questions.

V   Check references.

V   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.

V   Do not permit the use of sealants except
under unusual circumstances where  other
alternatives are not feasible.

V   Follow a preventive  maintenance pro-
gram of yearly inspections of your heating
and cooling system, regular filter changes,
and steps to prevent moisture contamination.
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