Extension and Ag Research News


Remove Mold for a Healthy Home

Killing mold isn’t good enough; it has to be removed, too.

Mold needs to be removed, not just killed.

Flooding and wet soil may cause basements, structural materials or building contents to become wet, which can lead to mold growth in homes, offices or other buildings.

“It is not healthy to live in a moldy environment,” says Ken Hellevang, North Dakota State University Extension Service agricultural engineer and flood expert. “Mold can trigger asthma attacks in people who have asthma, and exposure to mold is linked with coughing, wheezing and upper respiratory tract symptoms in otherwise healthy people.”

People can be allergic to mold and typically will have symptoms similar to other allergies, such as sinus irritation or congestion. Because people react to mold whether it is living or dead, the mold must be removed to create a healthy environment. Killing it using a biocide, such as bleach, or any other method of killing the mold is not adequate.

Because mold grows into porous materials such as carpet, wallboard and ceiling tile, you need to remove these materials. Washing will remove mold from nonporous materials such as metal, glass and hard plastic. After the surface is clean, it can be sanitized using a biocide, such as a chlorine bleach-water solution if desired, but remember that you must remove the mold, not just kill it, Hellevang says. Killing the mold does not eliminate the health hazard.

He does not recommend testing for mold except in rare circumstances, such as if requested by a medical professional. Mold test kits sold for home use will not provide accurate information. Some mold spores always are in the air, so petri-dish samples almost always will show mold growth and may cause undue concern.

In addition, no acceptable or unacceptable levels of mold spores have been established. Some people are concerned about black mold and will want to test to determine if what they have is the “black” mold. However, current research has not shown one type of mold to be of more concern than other types. Living in a moldy environment is unhealthy regardless of the type of mold.

The procedure for removing mold is the same for all types of mold. If you see mold or detect a musty odor, you need to remove the mold and correct the moisture problem leading to the mold growth.

Air cleaners or purifiers are not a substitute for removing the mold and correcting the moisture problem, Hellevang says. Mold spores settle on all surfaces, so air filters only remove some of the spores in the building. Also, do not use units that produce ozone in an inhabited building because ozone is a lung irritant.

Other units are being sold that purify the air through oxidation or by creating ions. These units do not remove mold, and the benefit of these units for a moldy environment is questionable, according to Hellevang.

Units with ultraviolet light also are being sold to improve air quality. Ultraviolet (UV) light can prevent mold growth if applied under very controlled conditions. However, the benefit of a UV light air cleaner or purifier is questionable.

Moisture from wet soil around a building will continue to enter the building until the soil is dry, and drying likely will take weeks. Monitor the relative humidity in the building using an electronic or mechanical gauge. Ventilate or dehumidify the building to keep the relative humidity at less than 70 percent to minimize the potential for mold growth.

The additional moisture in the air in the building may contribute to condensation problems when outdoor temperatures get cold. Ventilation may be required to keep the humidity below 30 to 40 percent during the winter to limit condensation.

To determine if moisture is coming through the basement floor or wall, tape a sheet of plastic that’s approximately 3 feet by 3 feet to the wall or floor for a few days and observe if moisture accumulates beneath or behind the plastic, or the concrete is darker.

Use a moisture meter to verify the wood moisture is at or below 15 percent before enclosing walls to minimize the potential for mold growth in the wall cavity. People living in homes that were rebuilt before the building was dried adequately have experienced respiratory problems months after the flood or water event occurred due to mold growth in wall cavities.

For more information on flood recovery, go to the NDSU flood information website at http://www.ag.ndsu.edu/flood. For more information on mold, go to the NDSU website at http://www.homemoisture.org/ and the Environmental Protection Agency website at http://www.epa.gov/mold/index.html.

NDSU Agriculture Communication -Sept. 6, 2011

Source:Ken Hellevang, (701) 231-7243, kenneth.hellevang@ndsu.edu
Editor:Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu
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