Dealing with Indoor Mould

 

What is mould?

Mould is microscopic fungi, a group of organisms which also includes mushrooms and yeasts. Fungi is highly adapted to grow and reproduce rapidly, producing spores and mycelia in the process.

You encounter mould every day. Foods spoil because of mould. Leaves decay and pieces of wood lying on the ground rot due to mould. That fuzzy black growth on wet window sills is mould. Paper or fabrics stored in a damp place get a musty smell that is due to the action of mould.

Mould, however, can be useful to people. The drug penicillin is obtained from a specific type of mould. Some foods and beverages are made by the actions of mould. Good mould is selected and grown in a controlled fashion.

Mould is undesirable when it grows where we don't want it to, such as in our homes. Over 270 species of mould have been identified as living in Canadian homes. Mould that grows inside may be different from mould found outside.

What makes mould grow?

Mould needs moisture and nutrients to grow. High moisture levels can be the result of water coming in from outside, through the floor, walls or roof; or from plumbing leaks; or moisture produced by the people living in the house through daily activities like bathing, washing clothes or cooking. Water enters the home when there is a weakness or failure in the structure. Moisture accumulates within a house when there is not enough ventilation to expel that moisture.

Different kinds of mould grow on different materials. Certain kinds of mould like an extremely wet environment. Other kinds of mould may be growing even if no water can be seen. Dampness inside the material can be enough to allow the mould to grow.

What are the health effects of exposure to mould?

In addition to often ruining surfaces and materials upon which it is present, certain strains of mould can also be quite damaging to our health. Indoor mould has been implicated in causing cold symptoms, headaches, difficulty breathing, skin irritation, allergic reactions and aggravated asthma symptoms. Pregnant women, infants, the elderly and those with respiratory problems or weakened immune systems are more susceptible to mould.

How do I know if I have mould?

Mould may be any colour: black, white, red, orange, yellow, blue or violet. Dab 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. Sometimes mould is hidden and cannot be seen. A musty or earthy smell often indicates the presence of mould. Even when you don't notice a smell, wet spots, dampness or evidence of a water leak are indications of moisture problems and that mould may follow.

White salt marks forming on concrete might indicate that excessive moisture is moving through the foundation. Get your weeping tiles checked by a professional.

How can I prevent mould?

Keep it out. Although mould usually develops due to the conditions outlined above, it can also be brought into the home on furnishings, potted plants, stored clothing and bedding material that we might bring in from outside. It's important that you check that items are mould-free before bringing them into your home.

Keep it clean. Old-fashioned housekeeping is the first line of defence against mould. There are no strict guidelines for how often to give your home a good scrub, but people who are more sensitive to allergens should clean more often, perhaps on a weekly basis, while others might be able to go two weeks between rigorous cleaning.

Keep it dry. You should keep humidity levels low in your home. Give your home as much ventilation as you can comfortably achieve. Opening windows when cooking or when taking a bath or shower helps to reduce the amount of moisture in the air and you should keep on top of any areas that are prone to condensation. Wipe down kitchen work surfaces regularly and clear up any spills or stagnant pools of water. If some materials cannot be completely dried (eg., drywall or insulation), you should replace them.

Keep it uncluttered. Don't store boxes up against concrete walls or floors. This could lead to moisture getting into the boxes and creating a haven for mould while damaging your goods.

How do I deal with mould and moisture?

Keep an eye out for leaks by identifying small pools of water, any discolouration or wet spots. Fridges, freezers, air conditioners and leaky washing machines are all easy targets and either a visible mould patch or a musty smell is usually the giveaway.

There are various products on the market that will help, such as fungicidal products. Wipe down affected areas with a fungicidal product that carries a Health and Safety Executive "approval number". Dry-clean mildewed clothes and shampoo mouldy carpets. Where possible, remove lining paper and wallpaper where you suspect mould growth, treat the plaster and then paint or paper the area again. After treating mould-affected areas, redecorate using a good-quality fungicidal paint.

If you have problems controlling mould or a family member suffers from respiratory or other health problems that appear to be aggravated inside the home, seek a professional by contacting your local Canadian Mortgage and Housing Corporation (CHMC). The CMHC can provide you with a list of individuals who have completed the CMHC Residential Indoor Air Quality Investigator program.

WHERE TO LOOK FOR MOLD

  • around and under plumbing fixtures:
  • sinks
  • tubs
  • toilets
  • showers
  • air-conditioners
  • heating systems
  • water-heaters

Leaks from outside are likely:

  • uninsulated outside walls
  • improperly sealed windows
  • cracks in siding
  • roof eaves
  • concrete slab cracks
  • unsealed building foundations