Gold Coast Magazine

How To Deal With Summer Mould In Your AC System

Mould can form anywhere and all year round. But if you’re a property owner, you may have noticed that these pesky fungi develop faster during the summer. That’s likely because of the high humidity and moisture levels during this time of the year.    

The fungi family boasts over 100,000 species, including healthy kitchen staples called mushrooms. But unlike their edible counterparts, mould may trigger specific health issues. These fungi produce irritants, allergens, and toxic substances, such as mycotoxins. (1) (3) 

Thus, health experts recommend homeowners to regularly check their properties for infestation. Consider the following guide if you spot mould formation near your air conditioning (AC) unit. But first, let’s find out how they develop indoors.

How does mould develop indoors? 

Mould grows on decaying matter and play a significant role in the decomposition process. They’re classified as fungi and reproduce through microscopic spores. These highly light spores are constantly floating in the air, especially outdoors. 

They can quickly enter the homes and latch on to wet surfaces. Apart from the key elements below, water and moisture are crucial in mould growth. (2)

  • Spores: Mould spores are ‘seeds’ that latch on any surface indoors or outdoors. They’re present everywhere and can’t be eliminated.  
  • Food source: Organic substances such as wood, fibre, and paper provide the nutrients that mould feed on. 
  • Ideal temperature: Warmer temperatures are typically conducive to fungi growth, and freezing temperatures can’t prevent them from developing, too.
  • Moisture: Mould can’t grow without moisture, and this must be complemented by prolonged condensation. Water leaks, condensation, and humidity can contribute to increased moisture. Scientists indicate that most mould species require at least 70% humidity levels.


Mould can develop quickly when you have all the components mentioned above. If you spot these unsightly discolorations, its important to act quickly before you have a full mould infestation on your hands. It’s advised to employ the assistance of professionals when it comes to removing mould effectively (and safely). Get in contact with Mouldmen or any other reputable mould remediation specialist to organise a free inspection and tailored treatment plan. 

Several household activities and natural occurrences could encourage fungi proliferation, making it almost impossible to mould-proof your home. These include roof damage, leaky plumbing, and condensation from cooking, drying clothes, bathroom use, and improper insulation.   

How to deal with mould in your AC 

Mould thrive in humid and damp environments, making air conditioning units an easy target. Apart from potentially sucking in spores from outdoor air, the internal mechanisms of a cooling system also warm up, promoting condensation. These are the two main reasons mould develop in your AC system, disrupting your slumber instead of helping you sleep better

Here’s how to properly deal with fungi formation in your air conditioning system. 

  • Turn off the AC unit

The United States Environment Protection Agency (US EPA) recommends that owners turn off the unit before doing anything. This action is mandatory for mould formed in a building’s heating, ventilation, and air conditioning (HVAC) system. (3)  

Using the AC despite spotting mould can spread the infestation faster, triggering various health symptoms, including allergies and irritation among the occupants. Different types of mould can develop indoors. Some types of mould can lead to respiratory issues, while a strain called Stachybotrys chartarum can trigger respiratory bleeding. (5)

  • Check the extent of mould growth

Before deciding who and how to get rid of mould, it’s essential to determine the scope of the problem. The EPA doesn’t prohibit property owners from performing mould removal themselves but suggests that professionals should handle any colony beyond 10 square feet in size. (3) 

Check online and offline sources for mould specialists. In some cases, these trained individuals may be able to provide advice on how to move forward and link you with reputable mould removal companies.    

If you’re comfortable with your skills and have a small AC unit, make sure you have the manual and a complete set of tools as well as protective gear. A mask or face shield and gloves are necessary to protect you from inhaling the spores. Use a flashlight to illuminate the inside section of the AC. Mould typically come in coloured formations of black, green, and brown, while another type of mould, mildew, may look greyish or slightly white. (4) 

  • Know when to D-I-Y or leave it to the professionals 

As mentioned, the EPA suggests property owners call in professionals to tackle mould infestation in surfaces over 10 square feet. However, considering the nature of HVAC systems, it may be challenging to measure. You may have better chances of doing it yourself if you only have a window-type unit.    

Skilled handypersons should also prevent doing it if the mould are likely caused by contaminated water or if you and any occupants have existing health issues. (5)  

When hiring a contractor, you must check the company’s background and ensure they’re experienced in getting rid of all types of mould. Also, ask for related certifications from government and private institutions.

  • Remove mould on your own 

Once your window-type AC is dismantled and after ensuring you have complete tools and protective gear, use a vacuum to clean the unit and wash the filter. You may use water mixed with bleach to wipe and scrub away mould streaks on the coils, ducts, and other visible areas. (4)    

Again, don’t attempt to clean HVAC ducts, as it can be highly challenging if done by inexperienced or untrained individuals. Besides, specific cleaning solutions need to be applied, and only cleaning companies have access to these products.   

  • Know when to replace your mould-infested AC 

If you discover that your air conditioning system suffers from significant mould infestation, it may be best to discard the unit and purchase a new one. If fungi formation has covered over one-third of your AC’s surface area, there may be a possibility of massive mould growth. In these cases, mould may have already covered a more significant part of your cooling system, and in places, you can’t see or reach with your cleaning tools. (4) 

When choosing a new AC unit, it’s vital to determine the ideal size and capacity, as an oversized cooling device will have issues getting rid of humidity and moisture. (1) 


Effectively removing mould in your AC system doesn’t mean your unit will be shielded from future infestations, as mould may have attached in areas you haven’t reached. As such, it may be better to seek the help of experts and take measures to prevent fungal growth further. 

There are numerous steps you can take to minimize moisture, humidity, and condensation from forming indoors and inside your cooling devices. Proper insulation and strategically placing your cooling units are two of the main steps. Keeping your unit regularly cleaned and serviced also helps prevent mould and increases its lifespan.


  1. “Mold Growth”, Source: https://energyresearch.ucf.edu/consumer/buildings/building-science-basics/mold-growth/
    1. “Mould and your health”, Source: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/mould-and-your-health
    1. “A Brief Guide to Mold, Moisture and Your Home”, Source: https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home
    1. “Solved! What to Do About Mold in the Air Conditioner”, Source: https://www.bobvila.com/articles/mold-in-the-air-conditioner
    1. “More Information on Mold”, Source: http://www.healthyairductcleaning.org/mold-remediation/mold-remediation-information/
How To Deal With Summer Mould In Your AC System

Gold Coast Magazine
Gold Coast Magazine

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