Every Time You Switch on Your Aircon, You Might Be Breathing Mould
You come home from work on a hot Melbourne afternoon, hit the aircon remote, and feel that cool air rush over you. What you do not feel — but might be inhaling — is a cloud of mould spores being blown through your ductwork and into every room of your home. For thousands of Melbourne families, ducted air conditioning systems are silently distributing mould contamination throughout their living spaces, triggering allergies, asthma attacks, and respiratory infections without them ever suspecting the source.
Why Mould Grows in Air Conditioning Systems
Your aircon creates the perfect environment for mould, whether you realise it or not:
- Condensation: The cooling process generates moisture on evaporator coils and inside ductwork. If this moisture does not drain properly, it pools and feeds mould
- Dust accumulation: Dust inside ducts is an excellent food source for mould. Combined with moisture, it forms a biofilm that supports extensive mould colonies
- Dark, enclosed spaces: Ductwork is dark, rarely cleaned, and has minimal airflow when the system is off — ideal conditions for mould establishment
- Temperature cycling: Switching between heating and cooling, or between on and off, creates repeated condensation cycles
Understanding the full scope of aircon mould contamination reveals why this is a problem that affects the entire home, not just one room.
Warning Signs of Mould in Your Aircon System
You cannot see inside your ducts, but these signs suggest mould contamination:
- Musty or stale smell when the system starts: A distinctive odour in the first few minutes of operation is the most common indicator
- Visible mould around vents: Dark spots or fuzzy growth on or around supply and return air grilles
- Black dust or residue: Dark particles collecting on surfaces near air vents
- Allergy symptoms that worsen indoors: Sneezing, watery eyes, throat irritation, or asthma flare-ups that improve when you leave the house
- Symptoms in multiple family members: When several people in the household develop respiratory issues simultaneously, an airborne source is likely
The Health Risks Are Serious
Mould in your aircon is not just unpleasant — it poses genuine health risks. When the system operates, it pressurises the ductwork and blows mould spores directly into the breathing zone of every room. This can cause:
- Chronic rhinitis (persistent runny or blocked nose)
- Allergic asthma attacks, especially in children
- Hypersensitivity pneumonitis (inflammation of lung tissue from repeated mould exposure)
- Recurring sinus infections
- Skin irritation and rashes
Children, elderly family members, and anyone with pre-existing respiratory conditions are especially vulnerable to mould-related health effects. If your family is experiencing unexplained symptoms, your aircon should be investigated.
What You Can Do
Regular Maintenance
- Replace or clean filters every 3 months (monthly during heavy use)
- Keep the area around the outdoor unit clear of vegetation and debris
- Ensure condensate drains are clear and draining freely
- Run the fan-only mode for 30 minutes after cooling to dry out the system
Professional Duct Cleaning
Standard duct cleaning removes dust and debris but may not adequately address mould. If mould is present, you need a specialist who combines duct cleaning with antimicrobial treatment and addresses the moisture source that allowed the mould to establish in the first place.
System Upgrades
Consider UV-C germicidal lights installed in the air handler, which kill mould spores and bacteria as air passes through the system. While not a substitute for cleaning existing mould, they help prevent recolonisation. For older Melbourne homes where mould allergies are a concern, this can be a worthwhile investment.
When to Get Professional Help
If you can see mould around your vents, smell it when the system operates, or your family is experiencing health symptoms, professional assessment is essential. A qualified specialist will:
- Inspect the full duct system using a camera
- Test for mould contamination with air or surface sampling
- Clean and treat the ductwork with appropriate antimicrobial agents
- Identify and resolve the moisture issue that caused the mould
- Advise on ongoing maintenance to prevent recurrence
We connect Melbourne families with experienced, insured aircon mould removal specialists who understand ducted systems and can restore your air quality safely. If you are also dealing with mould in other hidden areas, our guide to roof cavity mould covers another commonly overlooked problem area.
Take Action Today
Your air conditioning should make your home more comfortable, not make your family sick. If you suspect mould in your aircon ducts, the sooner you act, the sooner you can breathe easy again. Take our free mould risk assessment to evaluate your home’s risk and get matched with qualified mould remediation specialists who can inspect and clean your ducted system.