Offering cooling relief in summer and lovely warmth in winter, air conditioning is something many of us take for granted. But, like many things around the home, AC units need regular maintenance. Not just to keep them clean, but also safe.
You may not realise it, but air conditioners offer the ideal environment for mould to grow. And this is mould that can cause all sorts of health problems — from mild to serious. Here’s how to deal with mould in air conditioning systems.
Why does mould grow in AC units?
The answer is simple. Mould thrives in humid and moist environments — these are the basic building blocks of mould, and without them, mould couldn’t thrive.
Air conditioners essentially involve the circulation of air from outside your home, including the evaporation and condensation of moisture. But that air isn’t purified and contains lots of mould spores and other bacteria. When an air conditioner is turned off, its interior warms up. Any residual moisture and condensation within the unit, combined with oxygen, provides the perfect conditions for mould and mildew to grow and spread.
Why is mould such a health concern?
Not all moulds are created equal. Some are good (like the mould on your favourite camembert cheese), but others are harmful. Unfortunately, the ones that grow in air conditioning units are of the not-so-good kind. Mould in air conditioner units not only grows, spores can be released and become airborne and spread throughout your home.
Mould in air conditioner illness symptoms can include skin and eye irritation, a runny or blocked nose, and more serious respiratory problems for people who are susceptible to mould. These can include children, older people and the immune suppressed.
If left long enough, mould can also cause problems with the efficiency of your air conditioner. Mould build-up can lead to blockages within your AC’s drains and if not dealt with, can lead to more serious issues that can be inconvenient and expensive to fix.
How do I know there is mould in my air conditioner?
Mould spores are microscopic and often grow and spread undetected in air conditioning units for some time before they become visually noticeable. If you suspect you might have hidden mould growing in your AC unit, there are some tell-tale signs you can look out for.
The first is a strange, lingering smell that is typically musty, damp and unpleasant when the system is operating (some say it smells a bit like rotting food — not good).
However, mould in split system air conditioner units is often detected visually — this is the second obvious sign. It could appear as black mould in air conditioner systems or grey circular marks on the unit’s interior surfaces. Sometimes it can also appear as fuzzy or powdery and dark green in colour. In extreme conditions, mould can spread up the walls and onto the ceiling. That’s when you know you have a serious problem.
The third sign is health issues. As we’ve mentioned above, these can range from sneezing, coughing, a blocked nose, skin irritations and allergic reactions to serious respiratory issues.
How to prevent mould in your air conditioner
There is an old saying, “Prevention is better than cure”. And it is definitely the case when it comes to air conditioners. But maintaining your air conditioner doesn’t have to be an arduous task, just a case of some basic cleaning, plus having your unit serviced by a professional — and both should be done regularly.
As a general rule of thumb, the more frequently you use your air conditioning unit, the more frequently it should be cleaned, although every six months is a good guide.
Cleaning the unit yourself
How you clean your air conditioner depends on whether it’s a split system or a ducted unit. In both cases, it’s best to err on the side of caution and let the professionals do the job for you. That way, your unit will still be covered by its warranty. Plus, electricity is not to be messed with! Here are some tips on how to clean mould in air conditioner systems.
Cleaning a split system
Here is a step-by-step guide to cleaning a split system, including removing mould:
Turn off the electricity. Yep, it’s a no-brainer but an extremely critical first step. This includes turning off the power point your unit is plugged into, and the circuit board, if possible.
Read through the manufacturer’s instruction manual. If you don’t have one, you can generally download one online. This will give you basic instructions on how to clean filter panels, louvres and the exterior. It is not recommended you clean the unit’s condenser coils (that’s a job for the pros), as this can void your warranty or damage essential components.
Clean the exterior of both the interior and exterior units. A weekly wipe-down (with warm, soapy water or even clove oil mixed with warm water) can do wonders, including keeping mould spores and nasty bacteria at bay. This is important because many of the mould spores that circulate through your air conditioner come from the surfaces directly surrounding their intake. With the outdoor unit, ensure it’s free from anything like foliage, leaf debris and cobwebs that could obstruct its airflow.
Clean the filter panels. The above steps can reduce the number of mould spores that might get sucked into your air conditioner, but filter panels are the key to preventing dust and debris from entering your AC system. Mould particles are often attached to dust and debris, so filter panels have an important job! Keeping them as clean as possible will ensure your unit is not clogged and starved of air, so it will work more efficiently and ultimately lead to savings on your electricity bill.
To clean the filters, open the unit’s plastic cover and remove the panels. Take them outside and brush them thoroughly, then use your vacuum cleaner’s brush head attachment to suck up any lingering grime or mould. If it won’t budge, wash them in warm, soapy water (with a mild detergent) and completely dry them before putting them back in the unit.
Clean the louvres. These are the angled oscillating slats on the exterior of your unit, and they direct airflow. Give them a good wipe regularly.
Cleaning a ducted system
Cleaning and removing mould in home ducted air conditioning systems is a bit of a different story, as many of the components are located inside the roof cavity of your home. However, the ducted air conditioning filter is one element you can safely and easily clean yourself.
Undo the hinged return air grill frame fixings – these are usually thumb screws or sliding clips.
Open the filter frame and let it hang vertically.
Slide out the filter.
Wash the filter in warm water (you can also add a mild detergent).
Place the filter in the sun to completely dry out.
Slide the filter back into the hinged grill, swing the grill back into the recess and screw up the fixing screws or slide back the clips.
What NOT to do if you have air conditioning mould
Diffusers, scented candles and air fresheners will only mask the odour caused by a mouldy air conditioner. Anti-mould sprays are also not recommended as they can contain toxic chemicals that can get into your AC unit and become airborne and be inhaled, which can cause adverse health consequences.
Other chemical cleaners can be corrosive or caustic and cause long-term damage to the inner workings of the unit and shorten its lifespan. Using these may also void your warranty.
When to call a professional
Accessing all the potential hiding spots for mould can be a tricky process. It often requires an excellent working knowledge of the anatomy of your particular AC system. Some parts of your air conditioner where mould might form are also in areas that can only be accessed by a licensed and trained professional because of the potential for injury or even electrocution. And accessibility can be problematic without the right tools and equipment.
Businesses like ours will thoroughly inspect your unit and deal with any potential issues, including detecting and removing mould. Having your system regularly maintained by us can also stop a potential mould problem before it has a chance to take hold. This will ensure it is clean and sanitised, extend the life of your air conditioner, and potentially save you money on your next power bill!
- Karl Coppen, 2023, Found Mould In Your Air Conditioner? Here’s What To Do, Mould Men
- 2019, Quick & Easy Guide | How To Clean A Split Air Conditioner, H&H Air Conditioning