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 Air Quality Series On Air Duct Cleaning Part 3 Of 3

Air Quality Series On Air Duct Cleaning Part 3 Of 3

Preventing Air Ducts From Getting Wet

There should not be any moisture in your air ducts. The most effective way to prevent the growth of biological organisms in the air ducts is to control the moisture.

Moisture can get into your duct system by way of leaks or if the system was installed or serviced improperly. According to research, a major factor in the presence of moisture in a system may be condensation on or around an air conditioner’s cooling coils. Condensation develops when the temperature on a surface is below the dew point temperature of the air around the surface. If you have condensation or high relative humidity, it is more likely that you may also have mold growth in your ducts. Preventing moisture is not easy, but there are some things you can do, such as:

  • Repair water damage and leaks properly and promptly.
  • Ensure that your ducts are sealed and insulated in spaces in your house that are not air-conditioned, such as crawl spaces and attics. This will help keep the moisture caused by condensation from getting into your system. Keeping moisture out is important in order for your system to work as it should. The heating and cooling system has to be insulated properly in order to prevent condensation.
  • Check the cooling coils of your system carefully. Since their purpose is to remove water from the air, they can be a big source of moisture that gets into the system. You should ensure that the condensate pan drains as it should. If you see a lot of debris and/or standing water, you should suspect there is a problem and deal with it immediately. Also check for wet spots on the insulation near the cooling coils.
  • If you buy a new air-conditioning system, make sure that the unit you buy is the right size for what you need it to do. Also make sure that when it is installed, the ducts are sealed at the joints. If you get a unit that is too large for your needs, it will cycle off and on a lot, and therefore will not be efficient in removing moisture, especially in places with high humidity. Also pick a new system that has been designed to effectively manage condensation.

Using Chemicals And Chemical Biocides To Clean Air Ducts

Some air duct cleaning service providers may say that it is important to use a chemical biocide inside your ducts to kill fungi (another word for mold) and bacteria (or germs) and to keep these organisms from growing back. Some may also suggest using ozone, a highly reactive gas that is also a lung irritant, to kill these biological organisms. But there is a lot of controversy about whether ozone or chemical biocides are necessary and whether or not it is wise to put them into ductwork.

It is important to know that the EPA currently does not have any products registered as biocides for use on fiberglass duct board or ducts lined with fiberglass, so you need to find out if any part of your heating and air system contains either of these materials before you allow anyone to use a biocide in your ducts.

The EPA regulates chemical biocides under federal pesticide law. In order for a product to be legally used for a particular purpose, it must first be registered by the EPA for that use. The pesticide must have that specific use or uses and other important information on its product label. It violates federal law (and is therefore illegal) to use a pesticide in any way that is inconsistent with the directions on the label.

There are a few products that are currently registered with the EPA for use on the interior of air ducts made of bare sheet metal. There are also some products registered with the EPA to be used as sanitizers on hard surfaces (which could include ducts made of bare sheet metal). Keep in mind that while there are many products that may be legal to use on the inside of bare sheet metal ducts as long as you follow all directions on the label, not all of the label directions are necessarily appropriate for the use in air ducts. Some may actually be inappropriate; for example the directions might say to rinse the product off with water, but as stated above, adding moisture to the inside of the ducts could lead to the growth of mold.

You should not allow your service provider to apply a chemical biocide in your ductwork until he/she:

  • Shows you visible evidence that you have biological organisms growing in your ductwork. Showing you that microorganisms from your home grow on a petri dish (or other type of “settling plate”) is not appropriate. There will always be some microorganisms in the air and you expect some growth on a petri dish or the like. As stated above, it takes an expert to identify a substance as being biological and final confirmation may only be possible after lab analysis. Do not trust other test methods because they are known to not be reliable.
  • Explains to you why chemical biocides are necessary, instead of using brushing to remove the growth and moisture control to prevent further growth. If the physical methods (brushing and moisture control) can be done, they are the preferred methods.

If you do allow the use of a chemical biocide, your service provider should:

  • Show you the label on the biocide, which includes a description of the approved uses of the product.
  • Use the biocide only in areas of your duct system that are not insulated. This should be done after a proper cleaning to lower the chances that the mold will grow back.
  • Always use the biocide in strict accordance with the instructions on the product label.

Note: Although it may be legal for some products with low toxicity to be used while you and your family are home, it is a good idea to leave the home while a biocide is being applied to your air ducts for added safety.

Find an air duct cleaning service provider in your area.

For more information about how to hire the right pro for the job check out part one of this series and learn how to make sure that the job was completed thoroughly in part two of this series.

If you're unsure whether or not you actually need an air duct cleaning check out our FAQ: Do I need to have my home's air ducts cleaned regularly?

Photos courtesy of the EPA & InspectaPedia

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