Managing mould

The first step is to identify possible hazards. Find any existing mould and look at all the relevant things and situations that may contribute to mould growth in the workplace.

1. Inspect your business

   Inspect the workplace to identify areas where mould might grow. Do an audit for windows, air flow, and leaks. Assess ventilation and check air conditioning systems.

2. Talk to your workers

   Talk to your workers about possible mould issues, as they may see things that you overlook.

3. Review available information

Review the regulations, codes of practice and standards related to mould in the workplace. Look for trends in information already available, such as workplace records, inspection reports, sick leave, worker complaints, and compensation claims. Find out about possible risks from regulators, industry associations, unions, safety consultants, designers, manufacturers, importers, and suppliers.

Find more information on how to identify risks in How to manage work health and safety risks code of practice 2021 (PDF, 0.65 MB).

Identifying and assessing mould

The most obvious sign of a mould problem is visible mould. Mould can also grow in the dark, so check the back of wall linings, to top side of ceiling tiles, the underside of carpets and on roof materials in ceiling spaces.

Not all mould may be visible. Mould sometimes is detected by a musty, unpleasant odour. It can be in wall cavities, ceiling spaces or under carpets or floor coverings. Building materials such as plasterboard or carpets that become wet from leaks or flooding will eventually deteriorate if not dried out quickly.

So, look for mould whenever you have:

• musty smells
• visible mould growth
• flooding or water leaks
• a condensation problem.

Be careful when investigating mould as disturbance can spread it. Have personal protective equipment (PPE) available and use it if you find significant mould growth.

Mould can be difficult to identify as it comes in all colours and can blend with the material it's growing on.

Dormant mould looks dry and powdery, while active mould can look fluffy. Mould can also look moist or slimy with a distinctive musty smell. Some salts, surface dirt, and stains can look like mould. If unsure, the source is unclear or you have health concerns, get specialist advice.

Be aware of other health and safety issues when investigating mould, including:

• infection risks from flood recovery and response work
• hazardous chemicals
• asbestos
• confined spaces
• lead
• electrical hazards
• slips, trips and falls
• skin infections
• pests (such as rodents).

If you find mould, assess the size and extent of the mouldy area. Find the moisture problem or water source that allowed the mould to grow.

If you identify mould, or a situation where mould might develop, make a risk assessment to identify:

• if there is a risk to you or others
• whether any effective control measures are already in place
• what actions you could take to control the risk
• how urgently you should act.

A risk assessment can include looking at:

• the nature of the work and how this exposes workers and others
• whether the work is required or if it can be rescheduled to a time when the risk of exposure is reduced
• the frequency and duration of contact.

Use this risk assessment template (DOCX, 0.02 MB) to guide and record your assessments.

After assessing the risk, put suitable control measures in place. If an area is at risk of developing mould, take preventative steps. If an area already has mould, take the following action.

Treating existing mould (remediation)

1. Fix the cause

   Find and fix the water or moisture problem that is causing the mould growth.

   See specific guidance for healthcare to manage construction dust at healthcare facilities to protect vulnerable patients from mould exposure.

2. Clean the mould contamination

   Restrict access to the affected area and, where possible, schedule works for when the building is not being used.

   Dry out wet areas as soon as possible. Fans, wet vacuums, dehumidification units, heaters or air-conditioners on dry mode can help speed up the drying.

   Clean contaminated hard surfaces and materials using water and detergent (soapy water) or a vinegar solution. Dry completely. Clean tools and equipment after use.

   Discard porous materials (such as ceiling tiles, plasterboard, insulation and carpets) that can't easily be cleaned, have been wet for more than 48 hours, or have visible mould. Get professional advice about restoring valuable items.

   Learn more about dealing with mouldy records.

   Mould clean-up for small areas

   For less than 1m² of affected area:

   • Close doors and seal air vents where possible to prevent mould spores from spreading.
   • Have unprotected people leave the affected area during the clean-up.
   • Wear a P2 respirator (mask), gloves and safety glasses to scrub mould off hard surfaces with one of the following:
     • detergent and water or
     • three parts vinegar with one part water or
     • three parts alcohol (such as methylated spirits) and one part water.
   • Dry the material completely.
   • If the water has been present for less than 48 hours, you can dry out absorbent or porous materials. If they’ve been wet for longer, you may need to throw them away if they become mouldy as they will be difficult to clean properly.
   • Use wet vacuums, dehumidifiers and fans to help dry wet carpets and similar absorbent materials.
   • For valuable items that have been mould affected, get specialist advice.

   Mould clean-up for medium-to-large areas

   Medium jobs are where the area affected is 1–10m². Large jobs are where the area affected is more than 10m².

   For medium to large jobs, get professional advice. Professionals can solve the problem more quickly, make sure hidden mould is found, limit spread, and locate and fix moisture problems. Medium-to-large jobs also need extra controls to contain the mould, a greater level of PPE, and a higher level of consultation with stakeholders such as tenants or workers.

   Managing contaminated dust

   Manage dust to prevent mould spreading to other areas. Adjust the level of control measures to the extent of contamination and amount of disturbance.

   To manage contaminated dust:

   • Isolate the affected area:
     • Shut doors and windows leading to other work areas.
     • Seal supply and return air vents or shut down the HVAC system servicing the area.
     • Use floor-to-ceiling plastic sheeting with sealed edges.
     • For greater containment, set up a negative pressure enclosure and decontamination chamber.
   • Stop dust becoming airborne:
     • Use cleaning methods that minimise dust (for example, spray contaminated materials with a water mist or use an H-class industrial vacuum (PDF, 0.62 MB).
     • Avoid dry sweeping, household vacuums and compressed air as they create lots of dust.
     • Use ventilation controls. For example, fit power tools with H-class dust extraction use a HEPA-filtered air scrubber.
   • Contain mould-contaminated materials and debris before removing them for disposal or decontamination off site.
3. Inspect and evaluate

Once treatment has finished, inspect the site to make sure the mould risk has been addressed.

Consider using a professional service for this.

Preventing mould

Mould is not usually a problem in indoor environments unless a source of water or excess moisture allows it to grow. Mould growth in buildings can be prevented with good ventilation and by controlling excess moisture and leaks.

How to prevent mould:

• Keep building materials dry during construction.
• Make sure there is adequate drainage around buildings.
• inspect and maintain the building and its fixtures regularly. Check plumbing for leaks.
• Clean up wet areas and water damage promptly (within 24–48 hours).
• Remove stains from floors and carpets immediately using as little water as possible.
• Maintain heating, ventilation and air-conditioning (HVAC) systems. Set these to environmental conditions (for example, water-based coolers aren’t suitable in the tropics). Avoid running air conditioning with the windows open. Regularly check HVAC systems for signs of mould. Disinfect heating, ventilation and air-conditioning systems regularly.
• Manage water vapour and condensation, especially in areas such as bathrooms and showers. Turn on exhaust fans. Vent appliances that generate water (such as dryers) to the outside where possible. Insulate cold surfaces to prevent condensation.
• Limit indoor plants and fish tanks.
• Keep indoor humidity to between 30 and 50 percent. Open windows for good ventilation. Get a dehumidifier if the building tends to get damp.
• If you are repainting walls, consider using paint with anti-mould solutions added. Ask your painter or hardware store for details.

If you have excess water and moisture problems, get professional advice from a mould remediation specialist.

Risk management is an ongoing process. Check regularly to make sure the control measures are working. If you find problems, go through the steps again, review the information, and decide whether you need new controls.

Under the work health and safety laws you must review the controls:

• when you become aware that a control measure is not working effectively
• before a change that might create a new risk
• when you find a new hazard or risk
• when your workers tell you that a review is needed
• after a health and safety representative requests a review.

You can find a list to help you find any issues in the How to manage work health and safety risks code of practice 2021 (PDF, 0.65 MB).