Indoor air quality testing for mould usually means a spore trap air sample (and often a surface sample) sent to a laboratory, compared against an outdoor sample taken at the same time. It can show whether the air inside has more, or different, spores than the air outside on that day. It cannot tell you whether your home is “safe”, because no Australian or US health authority sets a safe level for airborne mould, and Australian health departments do not recommend testing when mould is already visible.
That makes air testing a narrower tool than most people expect. It is worth paying for in a handful of situations, mostly where mould is suspected but hidden, or where you need documented evidence. In most homes a moisture investigation that finds the source does more useful work for the money.
What air and mould spore testing actually measures
There are two common laboratory methods:
- Spore trap air sample. A calibrated pump draws a set volume of air through a cassette. The lab counts and broadly identifies the spores caught on it under a microscope. Results are reported as spores per cubic metre of air for that sample.
- Surface sample. A tape lift or swab from a specific patch tells you what that growth is, or whether a cleaned surface still carries residue.
A competent air test always includes an outdoor control, because outdoor air carries mould spores all the time. The useful result is the comparison: indoor counts well above outdoor, or spore types indoors that are rare outside, suggest an indoor source. Some practitioners also log temperature, relative humidity, carbon dioxide or fine particles (PM2.5) as part of a broader indoor air quality check; those readings describe the air, not the mould.
Why there is no “safe” spore count
The Western Australian Department of Health’s 2024 review, Indoor Mould: Health Risk Assessment and Management, states that there are currently no quantitative health-based exposure guideline values or thresholds for acceptable levels of mould exposure, and that a dose-response relationship between the amount of mould detected and health effects has not been established. The US EPA says the same of its own jurisdiction: there are no EPA regulations or standards for airborne mould contaminants.
In practice this means:
- A report cannot “pass” or “fail” a house against an Australian standard, because none exists. Be wary of any report that implies otherwise.
- Spore counts move with weather, season, open windows, vacuuming and recent renovation. One sample is one moment.
- A low indoor count on a dry, breezy day does not rule out growth in a subfloor or wall cavity that was not disturbed that morning.
What Australian health departments say about testing
NSW Health’s mould factsheet says that since most mould is visible, it is generally not necessary to test for mould in the home, and that an occupational hygienist can provide specialist testing where contamination is suspected but cannot be found. The WA Health review notes that no Australian jurisdiction currently recommends testing, and that sampling is not recommended for establishing health risk, although it may help determine the extent of contamination where hidden mould is suspected.
So the honest position is: testing is a diagnostic aid in specific cases, not a routine first step and not a health verdict.
When air testing is worth paying for
| Situation | Why sampling can help |
|---|---|
| Persistent musty smell with nothing visible | Indoor versus outdoor comparison can support a case for hidden growth before walls or floors are opened |
| After water damage or a flood | Elevated indoor counts can point to hidden growth in cavities or under floor coverings |
| A tenancy dispute, insurance claim or sale | A dated laboratory result adds independent evidence alongside a written inspection report |
| After large remediation work | Air and surface sampling forms part of post-remediation verification, comparing the treated area with outdoor or unaffected areas |
| A household member’s doctor has asked about the home | Documentation the GP or specialist can read alongside their own assessment, not a diagnosis |
When it isn’t worth it
- Mould is already visible. You do not need a lab to confirm visible growth is mould. You need the moisture source found and fixed.
- Mould keeps returning to the same spot. That is a moisture question; a mould inspection and moisture investigation using moisture meters, thermal imaging and humidity readings answers it, and a spore count does not.
- You only want a remediation quote. Scope and price come from the extent of growth and the cause, not from a spore count.
- You want to know if a particular species is “toxic”. Species lists do not translate into a health risk rating; that is a question for a GP.
Who does mould air testing in NSW
Check credentials yourself before booking. Two professional groups are relevant:
- Occupational hygienists, the specialists NSW Health refers to. The Australian Institute of Occupational Hygienists (AIOH) is the peak professional body and runs a consultant directory.
- Building biologists and mould testing technicians, listed by the Australasian Society of Building Biologists. Their assessments often cover more than mould; see the building biology assessment guide for how that differs.
Whoever you use, ask before booking: will they take an outdoor control sample, which accredited laboratory analyses the samples, and will the report explain the limits of the result rather than labelling the house safe or unsafe?
What a useful air quality report contains
- The date, time, weather and where each sample was taken, including the outdoor control
- The laboratory’s name and its results for each sample
- A plain comparison of indoor and outdoor results, with the stated limits of a single sample
- Moisture readings and photos showing where damp was found, because that is what drives the fix
- A recommendation tied to the cause: repair, remediation scope, or no further action
A report that offers only spore counts with no moisture findings tells you very little about what to do next.
What drives the cost
Illawarra Mould Removal does not publish a price for air testing, because it depends on the practitioner and the job. The main drivers are the number of samples (each indoor location plus the outdoor control), whether surface samples are added, laboratory turnaround, whether a full moisture inspection is done at the same visit, and how detailed the written report needs to be for an insurer, tribunal or buyer. Ask for the per-sample charge and the report fee separately so quotes can be compared. If you are deciding whether testing is worth it at all, the DIY kit versus professional testing guide covers the cheaper alternative and its limits.
Next step
If you have visible mould, a recurring patch or a smell you cannot trace, the starting point is finding the moisture. Use the contact form to describe what you can see or smell and your suburb; the enquiry is passed to an independent local professional who can say whether sampling would add anything or whether an inspection alone will answer the question.
Frequently asked questions
Does an air quality test tell me if my mould is dangerous?
No. There is no Australian health-based threshold for airborne mould, and the WA Department of Health notes that a dose-response link between spore counts and health effects has not been established. Health questions belong with your GP.
Is there an Australian standard for indoor mould spore levels?
No. The WA Department of Health’s 2024 review found there are no quantitative health-based guideline values for mould exposure, so a test report cannot certify a home against one.
Do I need air testing before getting a mould removal quote?
No. NSW Health says testing is generally not necessary when mould is visible, and remediation is scoped from the extent of growth and the moisture source rather than from a spore count.
Who should do indoor air quality testing for mould?
NSW Health points to occupational hygienists for specialist mould testing, and building biologists also offer it. Check they take an outdoor control sample and use an accredited laboratory.
Will air testing find where the mould is coming from?
Not on its own. It can suggest hidden growth exists, but finding the source takes a moisture investigation with moisture meters, thermal imaging and a check of the building envelope.