Mould - Frequently Asked Questions

What are moulds and where do they come from?

  • Moulds are microscopic members of the fungus family. Other types of fungi include mushrooms, mildew and yeasts.
  • They are found everywhere in our environment, both indoors and outdoors.
  • They play an important role in our outdoor environment, helping to decompose organic matter such as leaves and wood.
  • As mould grows it produces:
    • Mycelia, which are complex structures that can become visible to the human eye.
    • Spores, which are like seeds that can travel through the air to be deposited elsewhere.
  • The spores regularly enter the home in many ways:
    • through open windows or doors
    • on clothing
    • pets
    • food
    • furniture

top of page

What does mould need to grow?

  • Two conditions are essential for mould to grow: water and food (nutrients)
  • Certain types of moulds require an extremely wet environment, while others can grow with far less moisture.
  • Moisture can be the result of a number of problems, including:
    • Water coming in from the outside (failure in the roof, walls, or floor)
    • Plumbing leaks
    • Normal daily activities in the home which use water such as bathing, washing clothes or cooking.
    • Condensation on or within walls or floors due to drafts or improperly installed insulation.
  • Depending on the circumstances, mould can become established in as little as 48 hours.

top of page

Are moulds a health hazard?

  • Most types of moulds routinely encountered in homes and buildings are not a health concern for healthy individuals.
  • Some health effects have been shown to be caused by mould; others are more difficult to prove.
  • Health effects depend on:
    • the type of mould
    • the amount of mould
    • the production of certain substances by the mould
    • the degree of exposure
    • the health condition of the person exposed
  • Some people may be more at risk of having health effects when exposed to mould:
    • pregnant women
    • infants
    • the elderly
    • those with health problems such as respiratory disease or a weakened immune system

top of page

What are the health effects?

  • Allergies to mould may develop in up to 5% of the population. In sensitive individuals, allergic symptoms can include:
    • sneezing
    • runny nose, congestion
    • red, watery eyes
    • skin rash
    • increase in asthma symptoms (for those already suffering from asthma)
  • Mould exposure can also irritate the eyes, skin, nose, throat, and lungs, without triggering allergies.
  • Allergies and irritation symptoms will disappear once the individual (or the mould) is removed from that environment.
  • Certain types of moulds can cause minor skin infections such as athlete’s foot or jock itch. In rare circumstances, mould can cause more severe infections in people who have weakened immune systems. However, these health effects are not associated with mould growth in homes.
  • Consult your family physician if you believe there is someone who may be suffering from adverse health effects due to mould.

top of page

How do you prevent mould?

While we cannot eliminate mould in our environments, there are a number of basic steps you can take to prevent mould growth in your home. More detailed suggestions can be found by visiting the related links below.

  • Check your home regularly for signs of moisture and moulds.
  • Fix any water leaks, moisture or condensation problems promptly.
  • If water gets in your home, dry the area as soon as possible (within 48 hours to prevent growth).
  • Ensure sufficient ventilation is in use in rooms where moisture is generated such as bathrooms or kitchens. Fans and clothes dryers should exhaust to the outside of the home.
  • If necessary, use a dehumidifier to lower the relative humidity (below 60%, ideally 30-50%).
  • Reduce the amount of stored materials, especially items that are no longer used. Moulds grow on fabrics, paper, wood and practically anything that collects dust and holds moisture.
top of page

Should you get professional help to clean up mould growth?

The size of the affected area will determine whether you should clean and remediate the area yourself.

  • Small areas are no more than one square meter in overall size. This project could be undertaken by homeowners if they follow proper procedures.
  • Large areas are greater than one square meter in size. The Health Department recommends a professional be used for cleaning, preferably one that is experienced in mould cleaning and remediation. More detailed suggestions can be found by visiting the related links below.

top of page

What should you do to protect yourself and others when cleaning mould?

Cleaning and removing of mould may increase the amount of spores or other substances in the air, and expose you to direct skin contact with mould. Hence, the following items should be considered to protect yourself when cleaning mould:

  • Wear a disposable particulate respirator (for example, 3M 8210 or equivalent N95-level respirator), unvented safety goggles and household rubber gloves.
  • Isolation of the area to be cleaned is usually not necessary for small areas. However, such measures should be considered if sensitive individuals live or are near the affected area.
  • Isolation measures include closing of doors and taping the seams, or using plastic sheeting taped to walls and ceiling.
  • Infants and other family members suffering from asthma, allergies or other health problems should not be in the work area or adjacent room during the cleaning.
  • An exhaust fan blowing out of a window in the room being cleaned to the outside will help prevent contamination of other areas of the house as well as provide ventilation.

top of page

How do you get rid of mould?

In all cases, the first step in dealing with mould growth is to find the source of the moisture and remove it. If the mould returns after cleaning, then the source of the moisture is likely still there.

Cleaning and remediation procedures may be complicated or require special equipment. If you are uncertain about your ability to complete the task safely, it would be appropriate to request the assistance of an experience contractor.

Cleaning mould from building materials, furnishings and other items

  • Washable surfaces, such as tile or glass
    • wipe or scrub surfaces using a damp cloth and a solution of water and unscented detergent
    • sponge with a clean damp cloth
    • dry quickly and thoroughly
    • once dry, vacuum the cleaned surfaces as well as surrounding surfaces with a HEPA (high-efficiency particulate air) vacuum cleaner
  • Drywall
    • if the mould is on the surface of the paint, wipe the surface using a damp cloth and a solution of water and unscented detergent
    • dry quickly and vacuum with a HEPA vacuum cleaner
    • if the mould is beneath the surface of the paper covering, then it is best to replace the drywall
  • Carpets, fabrics and furniture
    • it may be possible to remove surface contamination from these materials (when dry) using a HEPA vacuum
    • use a wet/dry vacuum for wet materials and once dry, vacuum with a HEPA vacuum
    • professional drying and cleaning may be required
    • remove and dispose of these items if they cannot be effectively cleaned
  • Any material or item that cannot be effectively cleaned should be sealed in plastic and disposed of.

Following clean-up, seal and dispose of the contents of the HEPA vacuum and clean the washable parts of the vacuum.

Speed up drying by:

  • opening windows
  • using fans to blow air past the cleaned area or to force air out the window
  • use a dehumidifier to remove water from the air

top of page

top of page