• Mould is a type of fungi that lives on plant and animal matter.
  • Mould grows best in damp and poorly ventilated areas, and reproduces by making spores.
  • Airborne mould spores are commonly found in both indoor and outdoor environments.
  • For further information and advice on  mould issues, contact the Environmental Health section of your local council.
  • Before cleaning or disposing of water or mould-damaged items after a flood, always seek expert advice from your insurance company.
  • If you’ve decided to remove mould, make sure there is good ventilation and wear protective clothing.
Mould is a type of fungi that lives on plant and animal matter. This can include building materials like wood and gypsum plasterboard and furnishings like carpet and curtains and even books and boxes.  Mould grows best in damp and poorly ventilated areas and reproduces by making spores. Airborne mould spores are commonly found in both indoor and outdoor environments. When they land on damp spots indoors, they may begin to grow and spread. There is no practical way to eliminate all mould indoors; the way to control indoor mould growth is to control the source of moisture. It is important that your home has good ventilation to minimise internal moisture and prevent mould growth. 

What does mould look like

Mould is not always easy to recognise. It often looks like ‘fuzz’ or appears to be a stain, smudge or discoloration. The most common moulds are black, green or white. However, mould can be many other colours, ranging from grey to orange to brown and can also change depending on age or life-stage. 

How does mould affect health

Mould associated with damp buildings can trigger nasal congestion, sneezing, cough, wheeze, respiratory infections and worsen asthma and allergic conditions.

People who are more susceptible to these symptoms and other serious health effects include those with:

  • weakened immune systems
  • allergies
  • severe asthma
  • chronic, obstructive, or allergic lung diseases.

You should seek medical advice if you are concerned about the effects of mould.

What causes mould to grow indoors

Mould only grows when there is sufficient moisture on a surface or humidity in the air. Common causes include: 

  • leaky roofs and walls including and blocked gutters and downpipes
  • leaky plumbing
  • condensation from cooking, showering, clothes drying and from breathing inareas with poor air circulation eg cupboards and corners and furniture against uninsulated outside walls. Avoid conditions encouraging mould growth, by using heat, insulation and ventilation. The cheapest and easiest way of reducing moisture and humidity levels is by ventilating a room by opening a door or window. Use exhaust fans where available.

Actions you can take to reduce mould

The most important actions you can take to prevent mould in your home are those that minimise moisture. 

  • Fix leaky plumbing and roofs and other building faults
  • Ensure gutters are cleared and maintained
    • Reduce condensation by using exhaust fans, or open windows in the bathroom and kitchen when showering, cooking or using the dishwasher
    • Wipe up excess water caused by condensation such as on single glazed windows and on shower glazing
    • Air the home regularly by opening windows and doors on warmer days 
    • Vent clothes dryers to the outside and clean lint filters according to the manufacturer’s instructions.
  • Use reverse cycle air conditioning and or mechanical dehumidification if available
  • Ensure sufficient exhaust openings to the outside of the building if using evaporative cooling. Evaporative coolers increase the moisture content in indoor air, so the manufacturer’s instructions should be followed to ensure airflow in the home.
  • Maintain heating, ventilation and cooling systems (this includes regular servicing) according to the manufacturer’s instructions.
  • Use a vacuum cleaner with a HEPA (high efficiency particulate air) filter.
  • Avoid placing mattresses on the floor or surfaces without adequate ventilation.
  • Vacuum, and or turn mattresses if it can be done safely.
  • Increase air circulation around furniture by moving the furniture away from the walls.

Refer to information about cleaning up mould: refer to the information on the Better Health Channel website.

Rental properties with mould issues

When a rental property has mould, the owner should fix any mould caused by faults in gutters or other fixtures, but the tenant should ensure that extractor fans are used when available and the home is aired regularly where possible. 

Sometimes, the cause of the mould growth may be due to a building fault that may not be easily rectified.

If as a tenant, you have taken measures to make sure the building is properly ventilated and mould is still growing, you should raise the issue with the owner. 
Information on mould in rental properties is available on Consumer Affairs Victoria’s website.

Tenants seeking further advice on their rights can also contact the Tenants Union of Victoria on 03 9416 2577.

Testing for mould in your home

Where mould is visible, it is generally not considered necessary to test for it in the home. However, not all mould is visible, as contamination may be in cavities or the ceiling. Generally, if you can see or smell mould, you need to clean up and remove the mould immediately, as mould can damage surfaces it grows on.

If you suspect mould contamination but cannot find the source of the problem, or if you have already taken measures to prevent mould from growing and you are still having problems, you could employ an occupational hygienist or environmental health and safety professional. For a fee, these professionals can provide specialist mould testing and consultancy services.

Where to get help


After a flood: mould and your health Community information, 2010 Department of Health, State Government of Victoria, Melbourne. More information here.

More information


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This page has been produced in consultation with and approved by: Department of Health and Human Services - RHP&R - Health Protection - Environmental Health Unit

Last updated: October 2020

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