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Radon testing for Australian homes: a practical guide

Radon is a radioactive gas formed naturally as uranium in soil and rock decays. It is colourless, has no reliable smell, and commonly enters ground-contact rooms through cracks in concrete slabs, wall joints, service penetrations and gaps beneath floors. Soil gas is the usual source in Australian dwellings, although water and some building materials can also contribute.

Radon decay products can attach to airborne particles, be inhaled and damage lung tissue. Exposure risk increases over time, while smoking adds substantially to the danger. Australia uses 300 becquerels per cubic metre (Bq/m³) as the national action level for a dwelling’s occupied living area. A representative result at or above that level calls for assessment and exposure reduction.

Testing must establish whether radon is present in the lived-in part of a home and identify how high it rises under different conditions. A consumer monitor can provide a quick indication, while a properly deployed passive detector or professional monitor may produce a more representative result. Placement, duration, weather and building pressure all influence the outcome.

Owners, tenants and renovators need reliable evidence, even though their responsibilities differ. Renters should obtain permission from the landlord or property agent before installing equipment or changing the building. In a strata property, the body corporate may also need to approve work involving common services, ducts, ceilings or slab areas.

Radon and Australian homes

Radon levels can change significantly between neighbouring suburbs and even between rooms in one building. Parts of the ACT and eastern New South Wales are well known for elevated ground concentrations, often associated with particular rocks and soils. Elevated results also occur in Victoria, Queensland, South Australia, Western Australia and other locations, so an Australian postcode is not a reliable predictor. Local state or territory health and environment agencies offer region-specific advice, and some provide subsidised detectors or mitigation support.

Australian construction methods influence how radon enters a dwelling. Many contemporary houses use concrete slab-on-ground floors, with routes around pipes, wet areas, balconies and slab penetrations. Older homes may have suspended timber floors or under-floor spaces, while high-set houses can draw soil gas through cracks and cavities. Builders and radon remediation trades may use the terms sub-slab depressurisation and under-floor depressurisation for related systems.

A radon result does not produce dependable warning signs, so occupants should not wait for symptoms before testing. Nor is the action level a line between dangerous and harmless exposure; it identifies a level at which practical action is expected. Temporary precautions can reduce time spent in an affected room, but they do not remove the entry route or replace a properly designed remediation system.

Choosing a trustworthy test

A passive alpha-track detector is often the most representative option for an occupied home. It remains in place without power and measures accumulated exposure over a period commonly ranging from three to twelve months. That long duration helps smooth out seasonal and weather-related variation. Detectors can be installed in several rooms at once, although each one must be positioned according to its approved instructions.

Continuous active monitors provide readings over days or months, depending on the instrument and assessment. They are useful for quick screening, investigating a suspect room and checking whether a remediation fan is operating. A single short test can miss a period of high concentration, however. Consumer electronic monitors also vary in detector type, calibration and software, so their specifications and maintenance history deserve careful checking.

For a sale, lease decision, persistent concern or result near the action level, use a suitably qualified radon measurement professional. Accreditation requirements differ between states and territories, so ask what training, certification and laboratory quality controls apply. Request a written report showing detector position, exposure dates, equipment details, calibration status and the result in Bq/m³. Some devices display picocuries per litre; one pCi/L equals 37 Bq/m³.

Preparing the property for testing

Place detectors in the lowest frequently occupied area, especially where people spend many hours. Bedrooms, lounges and open-plan living spaces may matter more than a garage, roof space or rarely visited room. Keep equipment away from open windows, external walls, ceiling fans, fireplaces and direct air-conditioning outlets unless the manufacturer’s protocol states otherwise. Large or split-level homes may need measurements on more than one floor.

Follow the supplied testing protocol exactly. It may require doors and windows to remain closed for a defined period and air-conditioning or extraction systems to be switched off. Normal household conditions should otherwise continue, since creating an artificial pressure difference can produce misleading readings. Do not seal cracks, run a blower door or install a temporary fan merely to improve the result. Record unusual events, including open windows, combustion appliances, renovations and windy or wet weather.

Occupants must also provide safe access without moving belongings that could block the chosen location. Outdoor work may affect remediation access later. If an exhaust route or inspection panel must be installed near a deck, deck railing ideas can help coordinate the railing work while keeping the outlet unobstructed and discharging away from doors, windows and under-floor spaces.

Reducing radon after a high result

Do not begin by sealing every visible crack. A characterisation test first maps the affected floor and identifies important entry points, pressure relationships and suitable exhaust locations. This diagnostic stage prevents builders from treating only the most obvious gap while leaving another major route active. It also allows the remediation design to account for the home’s layout and existing services.

Sub-slab depressurisation is a common Australian solution for slab homes. A purpose-built fan draws radon-bearing soil gas from beneath the slab and discharges it outdoors through a safe, sealed duct. The outlet is normally located above the roof or another location that prevents concentrated radon from re-entering the building. Some houses use sub-floor extraction instead, while larger or complex buildings may need a combined approach.

Sealing can complement extraction by reducing pressure differences and closing secondary pathways, but it should not be the sole strategy. Ordinary mechanical ventilation and HEPA filtration generally do not remove radon gas, and increased air movement can sometimes draw more soil gas into the house. Carbon-based systems need appropriate design and replacement schedules. For Australian households undertaking a kitchen refresh at the same time, Vietnamese kitchen colours can inform cabinet and splashback choices while the mechanical layout is coordinated.

After installation, check the system, airflow and warning indicators, then commission a verification test under comparable conditions. A representative post-remediation measurement often runs for several months, allowing a meaningful comparison with the original result. Testing only immediately after a fan starts cannot demonstrate how the finished home will perform through a full seasonal cycle.

Planning a practical testing response

Before commissioning a test, use a clear testing sequence:

After receiving the report, respond to the measurement method and duration rather than an isolated alarm reading:

These methods serve different stages of the assessment:

Method Best suited to Main advantage Main limitation Evidence to request
Passive alpha-track detector Long-term average in occupied rooms Runs without power and integrates changing conditions Takes months and depends on correct placement Exposure dates, location, detector specification and Bq/m³ result
Continuous active monitor Rapid screening or trend monitoring Shows daily variation and fan performance Cost, power and calibration requirements Daily readings, calibration certificate and averaging period
Consumer electronic monitor Initial owner or renter screening Immediate result and repeatable checks Variable accuracy and limited whole-home coverage Model, calibration history, placement and unit conversion
Characterisation assessment Confirmed elevated result or pre-remediation planning Identifies entry routes and pressure conditions Requires a trained professional and more equipment Room-by-room results, building assessment and remediation plan
Verification test Checking completed remediation Demonstrates whether exposure has changed May require another extended measurement period Comparable test conditions and before-and-after averages

Book a properly planned radon test for your home today, record the result in writing, and schedule any required mitigation and verification before finishes or furnishings make access difficult.