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What Is It? How To Get Rid Of It?

Editor's Note: The following information was taken from Canada Mortgage & Housing Corporation (CMHC) publications "The Homeowners' Guide To Mould" and "Clean-Up Procedures For Mould In Houses."

What Is Mould?

Fungi are a group of organisms which includes such things as mushrooms, yeasts, and moulds. Moulds can cause allergies, asthma and other health problems. We encounter mould every day. Foods spoil because of mould, leaves decay and pieces of wood lying on the ground rot due to mould.

Moulds can be harmful or helpful, depending on where it grows. For example, the drug Penicillin is obtained from a specific type of mould, but some of the moulds that we find in our homes can be harmful to our health. Experts who have studied mould now say that "people should not live in mouldy houses".

What Makes Mould Grow?

Moulds will only grow if we provide them with moisture and nutrients (a food source). If we keep things dry, moulds can not exist.

High moisture levels can be the result of water coming in from the outside through the floor, walls or roof, or from plumbing leaks. Moisture is also produced by the people living in the home through such daily activities as showering, washing clothes or cooking. Moisture accumulates within the home when there is not enough ventilation (air movement) to expel the moisture.

How Can You Tell If It Is Mould?

One of the problems with mould is identifying it. Discolouration is one sign of mould, but it is important to point out that not all discolouration is due to mould. Mould may be any colour - black, white, red, orange, yellow, blue or violet. Here's a mould test for you to try. Dab a drop of household bleach (such as Javex) 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. Sometimes moulds are hidden and cannot be seen, but their presence is given away by a musty or earthy smell. And even when you don't notice a smell, wet spots, dampness or evidence of a water leak are indications of moisture problems and mould may follow.

How Can You Get Rid Of Mould?

The problem with mould occurs when it starts to grow inside the home. To eliminate an indoor mould and prevent reinfection, you must carry out several steps:

1. Kill off the mould spores and colonies at the contaminated sites by washing with a water, chlorine and detergent solution.
2. Clean any other surrounding sites that may be storing mould spores, so that they cannot continue to release spores and reinfect sites.
3. Find and eliminate the source of excessive water.
4. Keep surfaces cleaner than normal.
5. Provide continuous, controlled ventilation.

How Big Is The Mould Area & What Can You Do?

Mould is considered to cover a "small area" if it is no larger than the size of a standard garbage bag folded in half. You can clean up small areas of mould yourself. The minimum protective gear that you need to use when cleaning up any mould are:
- safety glasses or goggles;
- a disposable dust mask; and
- household rubber gloves.

Infants and other family members with asthma, allergies or other health problems should not be in the work area or adjacent room during the cleaning.

In cleaning up small mould areas on washable surfaces, scrub with a detergent solution, and then sponge with a clean, wet rag and dry quickly. When dealing with mouldy drywall, clean the surface with a damp rag using baking soda or a bit of detergent. Do not allow the drywall to get too wet. Mould that comes back after cleaning is usually an indication that a source of moisture has not been removed.

A "moderate area" of mould is larger than a garbage bag folded in half, but smaller than a 4' X 8' sheet of plywood. Follow the same precautions as listed above. Please note that a small clean-up should take minutes (not hours) to finish.

When using a bleach solution for clean-up, we recommend a solution of three parts water and one part bleach. It's also very important to remember that bleach fumes are harmful, so you should provide good ventilation and don't mix bleach with detergents that contain ammonia.

A "large area" of mould is one which is the size of a 4' X 8' sheet of plywood, or larger. If your mould problem is this size, or you experience a flooding problem or a sewer backup in your home, you should contact a trained professional for the clean-up.

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Last modified: June 22, 2003