Mould….What You Need To Know.

There’s serious talk around these days on mould, but just how much do you really understand about the nature and consequences of it?

Resisting mould from growing (in any indoor built environment – our homes, workplaces, schools etc) remains one of the most important considerations for a healthier, safer setting in which to live.

Here we share some vital information people need to know about it, Advice that hails from our expert mould remediation specialists with over 15 years’ first-hand experience in dealing with mould in workplaces.  What you need to know about mould, conditions in which it thrives, what to do on discovering you’ve got a mould problem; how to prevent it coming back and much more.

Important thing with mould – is understanding just how it got there to address that too. 

While awareness grows of just how building systems operate during certain events like extreme heat and humidity, unfortunately so many workplaces sadly just aren’t equipped to keep indoor air quality safe and pollutant-free.



Mould is a living organism. Growing and reproducing best in damp, poorly ventilated areas, buildings and on materials. Looking much like a stain, in a variety of colours, really has similar needs to any other pest – a suitable surface to grow on, food (to sustain it; debris, organic fibres, paper, wood, carpet, food, insulation/ and a whole host of other sources) and moisture (for germination.)

Fig.1 Moisture content Bedroom wall. WME (Wood Moisture Equivalent) 15-17% =At Risk

Mould thrives in high humidity levels with warm temperatures; with available light, oxygen also playing a key role in formation of mould too. Tiny microscopic spores are released into the air, drifting around before settling on areas with the required conditions (water and nutrients) to fuel their reproduction.

These spores producing mycotoxins as they feed off decaying or dead materials.

Plenty of sources contribute to mould growth: cooking, washing, air and heat humidifiers, condensation, plumbing leaks (in & outside your building) and that list goes on…


Mould contamination is any presence of active growth (past or current) with potential to impact your health.   Some people are more sensitive to moulds than others, and there are no clear-cut definitions of mould-related illness either – making people far more concerned about wanting to recognise the signs in themselves, family members or work colleagues.

Institute of Medicine (IOM) in USA, has found evidence linking indoor exposure to mould with upper respiratory tract issues, coughing, wheezing etc, in otherwise healthy people.

Effects of mould can range from benign to severe – pathogenic, toxigenic and allergenic.

Even random workplace mould occurrences (in homes too) could be dangerous to people; esp. if they’re highly susceptible (recovering from ill health, elderly, low level immune systems etc).

Airborne mould can be inhaled; people exposed in other ways too, apart from breathing in those mould spores from the air – skin contact, handling items that are mouldy and eating without hand-washing etc.

Some moulds are incredibly destructive too (like dry rot fungus and serpula lacrymans).  Mycotoxic effects from fungus to Organic Dust Toxic Syndrome (which presents as ‘flu-like’ symptoms.)   Allergic reactions, inhalation of spores, by touch, exacerbated asthma (mould spores trigger and worsen asthma), even hypersensitivity pneumonitis can be developed following acute or chronic exposure.   Not to mention all those other opportunistic infections which tend to follow invasion into an immune-compromised host.

If you encounter any type of mould issue in the workplace – it is paramount to introduce a treatment/ remediation plan fast.

IAQ and Poor Ventilation


Indoor air pollutants are one of the world’s top five environmental health concerns.

In our earlier Blog we wrote extensively about Indoor Air Quality and its direct connection to mould.  At this time of year, especially, many discover they have a mould problem – very often, a mould issue generated by their HVAC / air-conditioner.

Building owners, facilities managers etc regularly inform us their systems struggle to perform, even under normal operating conditions – but how many of those units are competently inspected, maintained from hygiene AS/NZS 3666 Microbial Control aspect either?

Doing much more than only keeping temperatures consistent, HVACs impact on people’s productivity levels, health, safety and energy costs.

What’s now understood about HVACs and air conditioners is they are the greatest pathways for pollutants inside any building (commercial or residential.) 

Evidence points to more than 50% of mould issues being caused/ encouraged by HVAC systems, because they’re near-on perfect feed systems and places for active mould growth. HVAC units which aren’t properly serviced or left unclean create far more condensation than usual, resulting in moisture build-up.

Throughout our careers as IAQ specialists having worked with mould in buildings for years, early on, we did encounter tremendous denial…. “no. we don’t have a mould problem!”Building owners running their AC at 23-24˚ thinking well, there aren’t any complaints so everyone’s happy right?  Not…

Fig 2. Contaminated HVAC ductwork (consider….people are breathing this in.)

Interesting how auto-service companies even understand the importance to decontaminating your car’s AC when it goes in for a service. But as recently as 4 years ago, most people had no idea of the impact that air conditioners were/are having on mould growth, vivid role they play inside buildings, in vehicles, as perpetrators of mould.

Hygiene aside; preventative maintenance programs are important to keep any HVAC system functioning properly and efficiently. Without regular, routine maintenance it is apt that a minor HVAC problem may well turn into a major repair exercise; notwithstanding the expense, also making major system failure a very real reality.

Extends also to addressing dirty, clogged filters. Apart from all the associated health threats; dirty, worn filters drain energy from a HVAC forcing it to work much harder, which increases your power costs and reduces the system’s life. Frequent monitoring and replacing filters improves not only IAQ inside the building (keeping dust, allergens, air pollutants at bay), it will help to optimise HVAC system performance too. Estimated well performing HVACs incl. components of that system can generate power savings in vicinity of 10-15%.

Keeping your HVAC systems clean, changing out air conditioner filters regularly (monthly), draining off excess water, cleaning pans are all good practice. As with regular checking for leaks and for random substances growing on or around air ducts, drip pan or intake vents – because if there is….likely to be a mould infestation there.

As for condensation lines, they too troublesome; not only because mould will grow there, but excessive no. of spores are blown right through a workplace or home, every time that HVAC is switched on.

Our best advice? Have HVAC and duct work cleaned by professional remediators at least 1-2 times per year in line with AIRAH guidelines and best practice (ASHRAH USA) and for good HVAC hygiene.

Fig 3.     Contaminated HVAC Air Supply Diffuser found in a school recently (discovered when supply vent was removed and subsequently rectified.)

Properly trained hygiene specialists identify HVAC performance problems (sometimes before they happen) and correct these, so your equipment performs as it’s been designed to do.


Ok, so let’s talk moisture (water).

Buildings leaking hot moist air and/or allowing moisture ingress into the indoor environment, are huge contributors to mould. Affects humidity levels, which in turn produces yet more condensation (underlying driver to mould growth.)

So critical is to eliminate that moisture source. 

  Fig 4.  Classic example of moisture/ water ingress left unresolved and turning into mould.


Rarely is mould treated in manner it should be; not seriously addressed. People clean down their walls; lo’ and behold – there it is again!

Physical removal of mould  from affected surfaces/ areas is best way to interrupt the mould life-cycles. Cleaning down surfaces in the correct manner, to be able to change the surface conditions is so important. Only treating surfaces across the entire environment prevents mould spores from re-populating other areas

Should you discover condensation or moisture collecting on windows, walls or pipes – act fast.  Never try to remove mould (….even a small area) without proper protection. Dry off wet surfaces, reduce moisture where you can, try to identify the water source?  Wet or damp materials (if dried in 24-48 hours of a leak) will not, in a lot of cases get the opportunity to grow mould. Meanwhile with overly saturated wet carpet or furniture which can’t be realistically dried off well, in that time frame, call on specialist assistance, team to carefully treat the area; decontaminate and remediate.

Yet another consideration: when undergoing building fit-outs, supply grills are changed out, forgotten is the existing, old (contaminated) rigid or flexible ductwork. No surprises, spreading mould spores into a newly instated area, the very minute the AC or HVAC is switched on…

Fig. 5 Photo of contaminated split system AC


Mould is often hidden in areas we don’t always think to look. Know that musty smell you occasionally encounter – would indicate there’s microbial growth somewhere (despite absence of obvious signs of infection or any visible mould growth.)


Look for:

·        Water incursion;

·        Visible signs of mould (white, black, green, pink, slimy appearances);

·        Smell, random out-of-place mustiness;

·        Any indication of lethargy or human sensitivities at work or at home – itchy eyes, burning sensations on skin, changes even in a person’s breathe patterns, other ailments reported by occupants; and

·        If workplaces, buildings or homes have been water compromised then look for discoloration, high RH (above 60%), be aware of construction defects, improper / unclean venting, HVAC, plumbing issues etc.


Mould is a four-letter word no building owner or home owner likes to hear. Be confident by getting qualified, knowledgeable, safe remediators onto your mould challenge.  There’s those operators around who after attending a “two-day” workshop on mould remediation then go around calling themselves “mould experts” – only fraught with danger.  Anyone can clean down a surface for mould using bleach or remove some gyprock.  And as building materials are extracted; those inexperienced operators are dispersing mould spores into the atmosphere and through your entire indoor built environment. Great care must be taken in the process to contain and eradicate mould.

Getting to the Roo Cause of Mould

Remember too, mould spores can stay dormant; no person could tell its age, how long it has been there or its current state. And mould can begin to grow again once it has all right conditions (moisture, warmth and food.)

Sound mould practices deal not just with symptoms – mould experts primarily focus on identifying and mitigating the cause of it:

–         First we assist to locate the Infestation (where is it? In the attic insulation, wall cavities? Between drywall’s, the basement ceilings, floors upstairs?)  Often lurking in places you would not suspect.…

–         Analyse it – hidden mould needs to be identified. Is it toxic mould or not? With infection control testing, measurement is key – and there’s quite a few different methods, and a process to this; every day science still developing on mould testing too.

–         Remediate; removing it safely, securely before we finally get down to Decontamination & Reinstatement of an entire area.

Keep these factors top of mind when warding off mould infestations:

I.           Keep it dry / keep the area clean;

II.           If you find mould – don’t ignore the problem because it isn’t going away (and most likely it will get worse);

III.          Never use Bleach. Does not kill mould or manage to penetrate porous surfaces, only whitens mould so it looks less visible to us. Cleansing with bleach won’t rid a surface or surrounding areas of floating spores either.  Basically, it is such an ineffective (dangerous) way to treat mould, with what’s a very corrosive chemical that can affect people’s health.

IV.          Another key piece of advice?   Next time you buy a home, along with White Ant certificate, it is prudent to have the property inspected for water/ moisture, investigate it previous history, check for any water ingress scenarios in its past?


Most worrisome is, that there are no standards in relation to mould in Australia and most other countries. Only just best practice (which is altering constantly as more is learnt about science of mould and its characteristics in the built environment.)

In Australia, we tend to rely on Guidelines from ASHRAH and AIRAH – IICRC 500/520 Water and Mould Guidelines being those ones we will work from. However, much more discussion (action) is required on the strategy and degree of understanding of resilience (Approach & Means used to address these hazards; mould or otherwise.)

While larger asset owners are all over this topic; what this means for their business services – many other building & facility managers (projects) are still found wanting…..Yet to face the new realities of healthier indoor environments; criticality to redesign of existing hygiene maintenance practices, the changes necessary to better manage workplaces and their own hygiene agendas.