The Dangers of Mould

The ideal rate of humidity in the home is between 35% and 45% -- anything higher than this causes mould.

Mould growth is encouraged in the standing water of humidifiers or dehumidifiers,
water damaged materials or wet surfaces. Contaminated central air handling systems can also become breeding grounds for mould, mildew and other sources of biological contaminants. The central air conditioning then distributes these contaminants throughout the home.

Newer Homes, More Mould?

Damp, mouldy homes are becoming more of a problem in recent years, according to the Canada Mortgage and Housing Corp. Tightly-sealed, energy-efficient homes make our indoor environments more prone to contamination by moulds, spores, fungus and mildew. Tighter homes can also keep moisture trapped inside.

How Mould Affects Us

While some moulds are benign, others are quite toxic. Mould can suppress the immune system. One can become immediately sensitized and develop allergies upon contact with large areas of mould growth.

Different species of mould have different potential health effects. Pathogenic moulds are those that can cause disease in humans. Bird and bat droppings are often infected with pathogenic moulds and are a special concern in renovation and demolition of older buildings.

Toxigenic moulds
are those that contain potent poisons (mycotoxins), usually on the surface of the spores. Symptoms associated with toxigenic molds include headache, sore throat, cough, skin rash, flu-like symptoms, nosebleeds, fatigue, fever, etc.

When spores are airborne or the fungal mass is disturbed, an occupant with pre-
existing allergies to moulds will react with running nose, eye and throat irritation, cough, etc. Prolonged exposure to mould in buildings may result in development of allergies in individuals who did not have allergies to mold before. Asthmatics are at risk of reacting to indoor mold with more frequent and severe attacks.

Remember, the spores of both pathogenic and toxigenic moluds can be harmful even after the mold colony has stopped growing.


Based on an article by Caroline David, Five Seasons Comfort / Electro-Air Canada