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Environmental and Workplace Health

Mould: Get Rid of It!

Health Canada recommends that all mould, regardless of the species, be cleaned and that the underlying water or humidity problem be dealt with quickly to prevent potential health issues.

Do I Need to Test for Mould?

You should first look for obvious signs of mould growth like:

  • Stains or discolourations on floors, walls, window panes, fabrics, carpets and other indoor surfaces.
  • A musty, "earthy" odour.

In most cases, there is no need to measure the actual concentration of mould in your indoor air, or to determine the specific species of mould that may be growing on indoor surfaces. Although possible to measure, the results of such tests are not really useful for a number of reasons:

  • The concentration of mould spores in indoor air will vary widely over time.
  • There are different types of mould species and each has its own level of potency, or impact on human health.
  • Different people have different levels of sensitivity to the various types of mould.

Not all mould is obvious. It can also grow inside walls or above ceiling tiles, so it is important to check for the presence of mould anywhere damp or moist, and especially where water damage has occurred.

If you suspect a mould problem that you cannot solve on your own, Health Canada and the Canada Mortgage and Housing Corporation (CMHC) recommend that you contact a trained Indoor Air Quality Investigator for advice on building-related aspects of air quality. These investigators can do a visual inspection to identify areas of concern and make recommendations for improving the situation.

How to Fix Mould Problems?

If you discover mould, follow these two steps:

  1. Clean the mouldy surface with water and dish detergent. There's no need to use bleach.
  2. Fix the underlying cause, whether due to water damage or excessive humidity.

You can generally clean small and moderate areas of mould by yourself, but you should consider getting professional help with extensive mould growth.

The CMHC classifies the amount of mould as

  • Small, if there are 1 - 3 patches, each less than 1 m² (10 square feet) in size
  • Moderate, if there more than 3 patches or if the patches are greater than 1 m² but less than 3 m² (32 square feet)
  • Extensive if the patch is larger than 3 m²

When removing mould, you should wear proper protective equipment, including rubber gloves, eye protection and a dust mask. You may also want to isolate the area by taping plastic sheeting to walls and ceiling to prevent the spread of dust and mould particles. Sensitive individuals should not be in the same or adjacent rooms during the work and may choose to leave the house until the mould is removed.

You might consider hiring a professional if there is a large amount of mould or if the mould keeps coming back after you clean it. A large amount of mould is often also the result of a larger problem, such as a leak in the foundation or a major flood, which may require professional help to fix.

How Do I Prevent Mould Growth?

  • Repair basement, roof and pipe leaks as soon as you notice them.
  • Keep your house or apartment dry by always using the kitchen and bathroom exhaust fans. If you don't have any fans, open the windows for a short time to re-circulate the air. However, damp outdoor air will not help dry the inside, and can spread the moisture to other parts of your home.
  • Make sure that clothes dryer hoses are properly connected and vented to the outside.
  • Ensure your tubs and sinks are properly sealed to prevent water from getting into the walls.
  • After a flood, or any type of water damage, be sure to completely dry the flooded area within 48 hours.
  • Measure your indoor humidity level with a Next link will take you to another Web site hygrometer and keep the humidity at around 50% in the summer, and 30% in the winter. If necessary, you can use a dehumidifier to reduce the relative humidity.
  • Discard clutter and excess stored materials. Mould can grow on fabrics, paper, wood and practically anything that collects dust and holds moisture.
  • Keep your house or apartment clean by vacuuming regularly.
  • Don't over-water your plants, and watch for signs of mould in plant pots.
  • Next link will take you to another Web site CHMC Fact Sheet: After the Flood - A Homeowner's Checklist

What if I Am a Tenant?

If you rent your home or workspace, there's a limit to what you can do to correct mould problems. If your landlord is unaware of the structural building problems that cause mould, direct him or her to some of the resources available on this site.

Landlord and tenant's rights and obligations fall under provincial and territorial jurisdiction. Ideally, you and your landlord will be able to come to an arrangement to deal with any problems, but information on dispute resolution in landlord/tenant issues is available if required:

Tips for Selecting a Mould-free Apartment

There are a lot of things to consider when looking for a new apartment, and if you are particularly concerned with the presence of mould, consider these factors:

  • Avoid basement apartments which tend to be damp and prone to mould-growth;
  • Avoid upper-floor apartments in buildings that have wet basements, since mould spores can circulate throughout the entire building;
  • Avoid apartments that do not have working kitchen or bathroom fans;
  • Avoid apartments with old carpets, or ask the landlord to change them before you move in; and
  • Avoid buildings that have a history of roof or plumbing leaks.