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HealthLink BC File #65b, July 2006

Indoor Air Quality:
Mould and Other Biological Contaminants





What are moulds?

Moulds are fungi that are found naturally both indoors and outdoors. Moulds spread by releasing tiny seed-like particles called spores into the air. Warm and damp conditions inside your home help mould to grow resulting in the presence of mould in indoor air.

What are biological contaminants?

Biological contaminants include mould, house dust, mildew, bacteria, viruses, animal dander, cat saliva, pollen, cockroaches and mites. They are either living things or produced by living things.

What health effects can moulds and other biological contaminants have?

Not all biologic contaminants cause health problems, but many are small enough to be inhaled. Some moulds and other biological contaminants can cause allergic reactions. Bacteria and viruses can cause infections, this can also occur with mould but is relatively uncommon. Some studies have found increases in common symptoms such as coughs, wheeze and headaches in people who live in homes that are damp and have visible mould growth.

Why do moulds grow?

High indoor air moisture levels, or humidity, help mould growth. For example, large differences between inside and outside temperatures can cause water to condense on the insides of windows where mould may form. Leaks from pipes or from the roof can also lead to damp areas where mould can grow. Bathrooms or humidifiers that are not vented may also contribute to mould growth.

How do I know if I have moulds growing in my home?

Mould growth may appear on damp surfaces such as windowsills or the inside of poorly insulated walls. Moisture can also be present within the structure of a wall, such as wood or plywood, due to leaks in the roof or outside walls, leading to mould growth inside the wall. Moulds can also be found on or under water-damaged surfaces such as tiles and carpets. Moulds often give off a 'musty' smell.

What can I do to control moulds?

The key to control of mould is through moisture control. To prevent high humidity and condensation:

What can I do to control other biological contaminants?

For more information


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