What is Mould?

Mould is a common name for any fungus that grows on food or damp materials. It can be black, white or almost any colour. In some cases, you may be able to smell the mould but not see it.

It then releases “spores” into air, which people can eventually breathe in. The longer the exposure to mould particles, the more it can negatively affect your health.

Where does mould grow?

In order for mould to grow, it needs moisture and a material it can live on, such as on drywall, windows sills, carpeting, ceilings tiles, and wood products.

Common areas where you can find mould in your home may include the wall or floor next to the bathtub or shower, under the kitchen or bathroom sink, in the basement, and other damp places.

What are the causes of mould growth?

Some of the causes of mould growth are:

  • Floods
  • Leaking pipes
  • Leaking roof
  • High humidity
  • Sewage backup

What are the health risks of mould?

Mould in your home can lead to wide range of health problems.  It symptoms are caused by the mould spores and the toxins it releases. Health risks depend on exposure, each person’s allergic sensitivity, and the mould species involved.

Some of the symptoms are:

  • Eye, nose and throat irritation
  • Coughing and mucus build-up
  • Wheezing and shortness of breath
  • Allergic reactions
  • Headaches

If you have any of these symptoms and suspected to have exposed to mould, see a health care professional.

Who is at risk?

Anyone can be affected by mould, but some people are more likely to be at higher risk than others. These people include:

  • Infants and children
  • Elderly
  • Pregnant women
  • People with weakened immune system
  • People with severe allergies or other respiratory conditions

How do I know if it’s mould?

There are two very easy ways to tell if a spot you see in your home is mould.


Mould often causes stains and can be any colour from black to red to yellow. However, not all stains are due to mould.  To tell if a stain is from mould, put a drop of household bleach onto a suspected spot. If the stain loses its colour or disappears, it may be mould. If there is no change, it probably isn’t mould.


If you detect a musty or earthy smell then there is a likelihood that mould may be present. If no smell is present, it doesn’t mean there isn’t any mould.  Not all mould smells.

If you suspect you have mould in your home or would like to determine the cause and extent of the mould, contact a professional mould inspector.

How do I prevent mould growth in my home?

Simple things you can do to prevent mould in your home:

  • Check home foundation, walls, windows, roof, plumbing, tubs and sinks for water leaks. If you see a leak or spill, dry the area quickly and fix the leak. Clean up immediately after any flood.
  • Check windowsills regularly for condensation or moisture.  If found, quickly dry the area.
  • Prevent high humidity by using air conditioners and dehumidifiers during humid weather, if possible.
  • Use kitchen and bathroom exhaust fans when cooking or showering. Let the fan run for a few minutes after you are done.
  • Do not install carpet around sinks and bathtubs/showers.
  • Throw out basement clutter. Cardboard boxes and old clothes are great places for mould to grow.
  • Regularly clean and disinfect anything that holds water, like humidifiers, de-humidifiers and air conditioners.
  • Keep your sump pump covered.
  • Install downspout extensions. Make sure they slope away from the home

I have mould in my apartment.  What do I do?

The first step to take is to inform your landlord or your building superintendent in the case of an apartment building. Don’t try to clean even small area of mould without your landlord’s permission. After informing your landlord, you can clean small patches (<1 m2) of mould on non-porous surfaces with unscented detergent and water.

Here are some links to information on how to clean up mould:

What is the role of the Health Unit?

The Health Unit does not conduct on-site investigations for mould complaints. The Health Unit also does not test or remove mould. If your landlord or superintendent fails to fix the problem, or mould comes back after repeated cleaning, contact your local municipal building department.

If you have any questions regarding mould, you can call 519-258-2146, ext. 4475 to speak with a Public Health Inspector.


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