Meth contamination thresholds define the surface residue level at which a property is considered contaminated and must be decontaminated. In New Zealand, two frameworks operate side by side: 1.5 µg/100 cm² under NZS 8510:2017 for non-rental situations, and 15 µg/100 cm² (contaminated) and 30 µg/100 cm² (uninhabitable) under the 2026 rental regulations for tenanted properties. Understanding which threshold applies to your situation is essential for landlords, buyers, and insurers.
The Current Threshold: 1.5 µg/100 cm²
Under NZS 8510:2017, the decontamination threshold is 1.5 micrograms per 100 square centimetres (1.5 µg/100 cm²). This means that if any surface wipe sample from a property returns a laboratory result at or above this level, the property is considered contaminated and must be decontaminated before it can be safely reoccupied. The threshold applies to all properties — whether contamination is from methamphetamine use (smoking) or manufacture.
This level was set based on toxicological assessments of the health risk posed by dermal contact, inhalation, and incidental ingestion of methamphetamine residue. It is deliberately conservative — set at a level that protects vulnerable occupants, including children, from chronic low-level exposure.
The 2026 Rental Regulation Thresholds: 15 µg and 30 µg/100 cm²
For rental properties, the 2026 Residential Tenancies regulations establish a separate set of thresholds under the Residential Tenancies Act:
- 15 µg/100 cm² (contaminated): At or above this level, a rental property is considered contaminated. Professional assessment is required, and the landlord must take action to address the contamination.
- 30 µg/100 cm² (uninhabitable): At or above this level, a rental property is considered uninhabitable. The property must not be occupied until it has been decontaminated and clearance testing confirms levels are below the threshold.
These thresholds are higher than the NZS 8510:2017 decontamination threshold of 1.5 µg/100 cm². The difference reflects the regulatory framework: the 2026 rental regulations are specific to tenanted properties under the Residential Tenancies Act, while NZS 8510:2017 is the broader industry standard used for non-rental situations including property sales, insurance assessments, and vehicle testing.
What the Threshold Means in Practice
When a meth test returns results below 1.5 µg/100 cm², the property is considered to meet the NZS 8510:2017 standard for habitation. When results exceed 1.5 µg/100 cm², the property must be decontaminated and then re-tested (clearance testing) to confirm that levels have been reduced below the threshold.
For landlords, a pre-tenancy baseline test that documents levels below the threshold is the foundation of a defensible property record. For buyers, a pre-purchase meth test that reveals contamination above the threshold gives you the leverage to renegotiate, require remediation, or walk away before settlement.
Which Threshold Applies to Your Situation?
The threshold that applies depends on the context of the testing:
- Rental properties (tenanted): The 2026 rental regulation thresholds apply — 15 µg/100 cm² (contaminated) and 30 µg/100 cm² (uninhabitable). These are used for tenancy disputes, rental property meth testing, and landlord-tenant matters.
- Property sales and purchases: NZS 8510:2017 applies — 1.5 µg/100 cm². This is the standard for pre-purchase meth testing and pre-sale vendor testing.
- Insurance assessments: NZS 8510:2017 applies — 1.5 µg/100 cm². Meth testing for insurance claims uses this threshold.
- Vehicles: NZS 8510:2017 applies — 1.5 µg/100 cm². Vehicle meth testing uses this threshold.
Property owners and managers should ensure that any testing they commission is conducted to the relevant standard and that results are interpreted against the correct threshold for their situation. When in doubt, contact EnviroCheck for guidance on which threshold applies.
What to Do If Your Property Exceeds the Threshold
If a meth test returns results above the applicable threshold — whether 1.5 µg/100 cm² under NZS 8510:2017 or 15 µg/100 cm² under the 2026 rental regulations — the property must be assessed and may need decontamination. This involves professional cleaning of all affected surfaces, followed by clearance testing to confirm the contamination has been reduced below the threshold. For a detailed guide on the process, see what happens after a positive meth test.
If the contamination is discovered during a tenancy or insurance claim, an insurance toxicology report may be required to support your position. For rental properties specifically, see our guides on rental property meth testing and pre-tenancy baseline testing.