Flood Information


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Removing Mold Only Safe Option

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 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.”

Killing mold using a biocide, such as bleach, or any other method is not adequate. Since mold grows in porous materials such as carpet, wallboard and ceiling tile, these materials need to be removed.

Washing removes 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.

Testing for mold is not recommended except in rare circumstances, such as if a medical professional requests the test. Mold test kits sold for home use will not provide accurate information, according to Hellevang. 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,” Hellevang says. “Living in a moldy environment is unhealthy regardless of the type of mold.”

The procedure for removing mold is the same for all types. 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. 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 that purify the air through oxidation or the creation of ions do not remove mold, and the benefit of these units for a moldy environment is questionable. Units with 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, Hellevang says.

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 in the wall cavity. People living in water-damaged homes that were rebuilt before the building was dried adequately have experienced respiratory problems months after the flood or water event occurred because of mold growth in wall cavities.

For more information on mold, visit www.homemoisture.org/, www.epa.gov/mold/index.html, www.ag.ndsu.edu/flood or www.extension.org/Floods.

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