Mold in Home? Here’s What You Need to Know

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Mold in homes is unsightly and could create serious health problems.

Small airborne mold spores or particles can be inhaled deep into the lungs. Inhalation of mold spores can lead to respiratory problems. Mold spores could be both toxigenic (i.e., have toxic effects) and allergenic. Mold is especially common in basements of old homes where moisture levels are high.

Discovering mold in homes causes panic in many people. Since you’re reading this now, you’re probably concerned about the possibility that your home could be having mold. Every home has some mold. It only becomes a problem when it actively grow in the home. The key to preventing mold in your home is to keep the indoor humidity low, that is, below 60%. Mold is likely to be present in any place in your home where water has been sitting for 24 hours or more or where it’s constantly damp.

Moisture as a contributing factor to mold in homes

Moisture infiltration is the main cause of mold growth in homes. Moisture may come from many sources. Moisture can enter structures via flooding, wet basements, plumbing leaks, improper landscaping design or poor maintenance whereby the masonry foundation/wooden structural base ends up underground leading to rot.

If your home is in a region where moisture is a common problem, in addition to the dehumidifier, you may want to consider installing an exhaust fan and open windows whenever possible to reduce the humidity indoors. Too much moisture in a home would definitely lead to mold growth and proliferation of other microorganisms. Indications of a moisture problem may include discoloration of the ceiling or walls, warping of the floor, or condensation on the walls or windows.

Mold growth in homes

As mentioned earlier, every home has some amount of mold in form of spores. Mold spores exist everywhere in the environment and can enter buildings and homes through open doors and windows, pets and even people. Once mold spores are inside they may settle on damp surfaces where they may begin to grow and reproduce more spores.

For significant mold growth to occur there must be a source of moisture (which could be invisible humidity), a source of food, and a substrate capable of sustaining growth. Mold growth can commence within 48 hours of water damage, if the water comes into contact with organic building materials and is not noticed or dried properly. All mold growth in homes is a direct result of elevated moisture levels in the materials that the mold is growing on. Mold growth from leaks can often be hidden.

Mold growth may be found on walls, ceilings and floor cavities. If mold growth occurs on porous or hard to clean material, the material has to be removed and replaced with new materials. In some cases, wood can simply be treated for mold growth with a biocide, then dried and sealed. If there is mold growth in your home, you should clean up the mold and fix any water problem, such as leaks in roofs, walls, or plumbing.

Mold growth can be removed from hard surfaces by cleaning with ordinary household detergents followed by drying. Check routinely for new mold growth or signs of moisture that may indicate the need for cleanup, home repair, or removal of affected materials. Sometimes, mold growth is hidden and difficult to locate.

Black mold in homes

Most molds in home appear black or shades of black. Therefore, the term Black mold does not refer to any specific type of mold. However, some people incorrectly use the term “black mold” to refer to Stachybotrys chartarum. Stachybotrys chartarum commonly grows in damp areas and appears black. “Black mold” has been the subject of hundreds of legal settlements and sizable awards in North America against builders, landlords, insurers and corporations.

Sampling for mold in homes

Samples can be taken by sticking a piece of clear tape on the surface suspected of mold growth and then mounting the tape on a plastic bag. Air samples can also be taken but air sampling requires specialized equipment.

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Dr Jackson Kung'u
Dr. Jackson Kung’u is a Microbiologist who has specialized in the field of mycology (the study of moulds and yeasts). He is a member of the Mycological Society of America. He graduated from the University of Kent at Canterbury, UK, with a Masters degree in Fungal Technology and a PhD in Microbiology. He has published several research papers in international scientific journals. Jackson has analyzed thousands of mould samples from across Canada. He also regularly teaches a course on how to recognize mould, perform effective sampling and interpret laboratory results. Jackson provides how-to advice on mould and bacteria issues. Get more information about indoor mould and bacteria at

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