Your Reading List

Make Sure All Mould Is Gone

Air cleaners or purifiers are not a substitute for removing the mould and correcting the moisture problem.

Flooding and wet soil may have caused basements, structural materials or building contents to become wet, which can lead to mould growth.

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

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

Since mould grows into porous materials such as carpet, wallboard and ceiling tile, these materials need to be removed. Mould can be removed from non-porous 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 mould must be removed, not just killed, Hellevang says.

Testing for mould is not recommended except in rare circumstances, such as if requested by a medical professional. Mould test kits sold for home use will not provide accurate information. Some mould spores always are in the air, so Petri dish samples almost always will show mould growth and may cause undue concern.

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

The procedure for removing mould is the same for all types. If you see mould or detect a musty odour, the mould needs to be removed and the moisture problem leading to the mould growth corrected.

Air cleaners or purifiers are not a substitute for removing the mould and correcting the moisture problem, Hellevang says. Mould 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 mould, and the benefit of these units for a mouldy environment is questionable. Units with ultraviolet light also are being sold to improve air quality. Ultraviolet (UV) light can prevent mould 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. 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 per cent to minimize the potential for mould growth.

To determine if moisture is coming through the basement floor or wall, tape a sheet of plastic that’s approximately 3×3 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 per cent before enclosing walls to minimize the potential for mould growth within the wall cavity.

About the author

North Dakota State University's recent articles

Comments

explore

Stories from our other publications