What is Mould?

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Mould is the common word for any Fungus that grows on food or damp building materials. It often looks like a stain and comes in a variety of colours. In some cases, however, mould may not be visible but may have a musty odour. If it is allowed to grow, mould can contribute to poor indoor air quality.

Washing, cooking, air humidifiers, condensation and leaks from the outside all produce the kind of indoor moisture that mould needs to grow. Also, poor ventilation contributes to higher humidity levels and leads to condensation, which also allows mould to grow.

In order to reproduce, moulds release small "spores" into the air and these spores are small enough that people can actually breathe them in. Mould spores are always present outdoors. So, when mould grows indoors, the number of mould spores and fragments is usually higher indoors than it is outdoors.

High concentrations of airborne mould spores can have a number of adverse health effects.

The Mould Equation

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Find Out More

• It's Your Health: Dampness, Mould and Indoor Air
• Fungal Contamination in Public Buildings: Health Effects and Investigation Methods
•  Health Risks Associated with the Indoor Presence of Moulds: Institut de Santé Publique du Québec (INSPQ) (PDF Version - 356 K)
•  U.S. Environmental Protection Agency: Mold Course