Extension and Ag Research News


Remove Mold for a Healthy Home or Other Building

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 our 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. Since 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.

Since mold grows into porous materials such as carpet, wallboard and ceiling tile, these materials need to be removed. Mold can be removed from nonporous materials such as metal, glass and hard plastic by washing. After the surface is clean, it can be sanitized using a biocide, such as a chlorine bleach-water solution, if desired, but remember that the mold must be removed, not just killed, Hellevang says.

Testing for mold is not recommended 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 is 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, the mold needs to be removed and the moisture problem leading to the mold growth corrected.

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, units that produce ozone should not be used in an inhabited building because ozone is a lung irritant.

Other units are being sold that purify the air through oxidation or the creation of ions. These units do not remove mold, and the benefit of these units for a moldy environment is questionable. 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 less than 70 percent to minimize the potential for mold growth.

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.

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 within 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 within wall cavities.

For more information on flood recovery, go to the NDSU Flood Information Web site at http://www.ag.ndsu.edu/disaster/flood.html. For more information on mold, go to the NDSU site at http://www.homemoisture.org/ and the EPA site at http://www.epa.gov/iaq/molds/moldresources.html.

NDSU Agriculture Communication

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