Thursday, Sep 27, 2012

What's that smell?
How to find and eliminate mould in your home

Although it’s not something we like to think about, we encounter mould every day. Foods spoil because of mould. Leaves decay due to mould. That black growth on wet windowsills is mould, and paper or fabrics stored in a damp place get a musty smell that is due to the action of moulds.

But not all mould is bad. For example, penicillin is obtained from a type of mould and some foods and beverages are made by the actions of moulds.

However, moulds are undesirable when they grow where we don't want them. Mould growing inside the home can pose a serious health risk, especially if you or anyone in your family suffers from asthma or allergies. But as long as you know where to look, what to look for and how to prevent or clean up mould, you should be able to keep any potential mould problems in your home under control.

Moulds are always found in the air outside and in all buildings. They come into the home in many ways: through open windows or doors, on clothing, pets, food or furniture. The problem starts when it grows inside the home. The presence of mould is a sign that there is too much moisture in your home – a situation which must be corrected.

Two signs of mould are discoloration and odour.

Although discoloration could indicate the presence of mold, this is not always the case. Carpeting near baseboards, for example, can be stained by outdoor pollution entering the home. Stains or soot may also be caused by the smoke from burning candles or cigarettes. Mould may be any colour: black, white, red, orange, yellow, blue or violet.

To determine if a stain is mould, dab a drop of household bleach onto a suspected spot in a discreet location (in case the bleach discolours the surface or material under the suspected mould). If the stain loses its colour or disappears, it may be mould. If there is no change, it probably isn’t mould.

Depending on the size of the problem, you may be able to clean it yourself (see the information at the end of this article). However, you may need professional help if there is a lot of mould or if it comes back after repeated cleaning, if your home is very moist and damp or if a family member suffers from asthma or respiratory problems or other health problems that appear to be aggravated inside the home.

Where to get help

If you do have an extensive mould problem in your home, you can seek advice from an expert (e.g. home inspector or indoor air quality consultant) with knowledge and expertise in this area.

To learn more about preventing and dealing with mould in your home, CMHC has a free About Your House fact sheet called “Fighting Mould.” To obtain your copy, visit us online at or call our toll-free number: 1-800-668-2642.

Mark Salerno is district manager for the Greater Toronto Area at the Canada Mortgage and Housing Corporation. You can reach him at 416-218-3479 or

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