Mould Sampling & Testing in Australia — Air Samples, Surface Swabs & Interpreting Lab Results
Who Conducts Mould Testing?
Mould testing should be conducted or directed by a qualified industrial hygienist (IH). In Australian restoration practice, the hygienist is typically engaged by the insurer or the building owner. The restoration contractor should not conduct their own clearance testing on jobs they have remediated — the independence of the IH is essential for the validity of the clearance. However, restoration technicians benefit significantly from understanding what the samples are, how they are collected, and what the results mean — because the hygienist's findings directly determine the scope of work.
Types of Mould Samples
### Air Samples (Spore Traps) Spore trap air sampling is the most common mould testing method in Australian restoration. A pump draws a measured volume of air through a cassette containing an adhesive-coated slide. Airborne spores and particles are impacted onto the slide. The cassette is sent to an accredited laboratory where the slide is examined under a microscope and spore types and concentrations are counted. Results are reported as spores per cubic metre (spores/m³). Spore trap samples are useful for assessing the overall airborne spore load, comparing indoor and outdoor levels, and monitoring pre- and post-remediation conditions. **Limitation**: Spore trap sampling identifies spores by morphology (shape), not by species. It cannot distinguish between viable (live) and non-viable (dead) spores, and it cannot identify all fungi — some genera produce few airborne spores. ### Surface Samples **Tape lift samples** (sticky tape pressed onto the suspected mould surface, then transferred to a slide) identify the type of mould present on a visible surface. They are useful for confirming the genus of mould on a specific material. **Swab samples** are collected by rubbing a sterile swab over a defined area of the surface and sending it to a laboratory for culture and microscopy. Culture-based methods can identify viable mould and grow out colonies for species-level identification — a more detailed result than spore-only morphology. **Bulk samples** involve sending a physical piece of the material (e.g., a section of plasterboard or carpet) to the laboratory for analysis. Bulk sampling is the most thorough method for confirming mould colonisation within a porous material.
Interpreting Results: The Comparative Outdoor Standard
There is no universally agreed 'safe' indoor spore count in Australia — the appropriate interpretation is comparative. IICRC S520:2024 uses the principle that indoor air quality is acceptable when the indoor spore count and species profile are broadly similar to the outdoor reference sample collected at the same time. A useful heuristic: if the indoor total spore count is less than 1.5× the simultaneous outdoor count, and no elevated concentrations of indicator species (Stachybotrys, Aspergillus/Penicillium in high concentrations, Chaetomium) are present indoors compared to outdoors, conditions are generally within the normal range. Elevated concentrations of certain genera indoors compared to outdoors — particularly Stachybotrys, Aspergillus, Penicillium, and Chaetomium — are indicators of active mould growth within the building and require remediation.
Post-Remediation Verification (PRV) Sampling
For formal post-remediation clearance, the IH should collect: 1. Indoor air sample(s) within the remediated area (after cleaning but before containment is removed) 2. Simultaneous outdoor reference sample 3. Indoor sample from an unaffected reference area within the same building Clearance is typically confirmed when indoor spore counts are at or below outdoor reference levels for the same genera, with no visible mould remaining on remediated surfaces.
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