Residential Air Duct Cleaning - Never Allow Chemicals!
Avoid cleaners who advertise the use of
biocides or sealers, here's why
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:
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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.
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Explain why biological growth cannot be removed by
physical means, such as brushing, and further growth prevented
by controlling moisture.
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If you decide to permit the use of a biocide, the
service provider should:
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Show you the biocide label, which will describe its range
of approved uses.
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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.
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Always use the product strictly according to its label
instructions.
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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 encapsulate 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 to
encapsulate contaminants in any type of duct. Instances when the use of
sealants to encapsulate the duct surfaces 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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