HAMILTON, NEW ZEALAND — 20 September 2026 — EnviroCheck Forensics, New Zealand's independent property methamphetamine testing authority, today published a new technical guide explaining why sampling technique — not just the laboratory result — is the single most important factor in determining whether a methamphetamine contamination assessment can be trusted.
The guide, titled "Why Meth Sampling Technique Matters", addresses a long-standing gap in public understanding: that two test results from the same property can tell completely different stories — not because the laboratory made an error, but because the samples were collected for different purposes and in different ways.
"A laboratory can only analyse what it receives," said Todd Sheppard, EnviroCheck's principal forensic assessor and author of Buried Truth. "If the sampling context doesn't travel with the sample — from the wall to the chain of custody to the final report — the result can be technically correct but practically misleading. That's how properties get wrongly condemned, and how contamination gets missed entirely."
What the Guide Covers
- The two distinct purposes of methamphetamine sampling — surface screening to confirm a property is clear, and intentional sub-paint sampling to investigate historical contamination beneath painted surfaces.
- Why a sub-paint sample is not automatically 'wrong' — it is collected for a different question, and that context must be documented on the chain of custody.
- What EnviroCheck records at every sampling location: surface type, sampling purpose, wipe area, solvent, and technician identity.
- How sampling context can be lost between the wall and the final report — and why that loss leads to unnecessary remediation costs and poor decisions.
Why This Matters Now
With the Real Estate Authority's 2026 methamphetamine disclosure guidance now in effect, buyers, sellers, landlords and property managers are making decisions based on methamphetamine test results more than ever. A result that lacks documented sampling context can trigger tens of thousands of dollars in unnecessary remediation — or, worse, miss contamination that a new occupant later discovers.
The guide is part of EnviroCheck's broader effort to build technical E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) and give property decision-makers the language to ask the right questions before commissioning or acting on a methamphetamine test.
Not a Criticism of Analytical Laboratories
EnviroCheck emphasises that this issue should not be interpreted as criticism of analytical laboratories. Laboratories generally receive a labelled sample, extract it, analyse it and report the result according to the information supplied by the submitting party. The condition of the wall, ceiling, door, cabinetry or other surface is normally outside the laboratory's direct control.
This means one of the most important quality-control points occurs before the sample reaches the laboratory.
EnviroCheck is encouraging laboratories, sampling companies and industry organisations to consider stronger documentation requirements for samples where paint fragments, coatings or subsurface material may have been collected.
Suggested Safeguards
- Checking and documenting surface condition before formal sampling.
- Photographing deteriorated, softened or unstable sampling locations.
- Using a simple surface-stability or blot check where appropriate.
- Avoiding compromised surfaces when the objective is to measure surface residue.
- Clearly identifying intentional sub-paint or subsurface samples.
- Recording unusual sample conditions on the chain-of-custody form.
- Ensuring laboratory reports retain relevant information supplied by the sampler.
- Distinguishing analytical laboratory performance from field-sampling quality.
Why It Matters
Methamphetamine results can influence significant decisions involving property remediation, tenancy, insurance, property sales and legal disputes. A laboratory result can be analytically accurate while still being difficult to interpret if the original sample does not represent what the reader believes was sampled.
EnviroCheck believes greater emphasis on field sampling integrity could improve confidence in methamphetamine testing while reducing disputes over unexpectedly high or inconsistent results.
The company has documented the issue extensively in Todd Sheppard's book The Buried Truth, which examines the development of New Zealand's methamphetamine contamination testing industry and the relationship between sampling practices, laboratory analysis and property decisions.
A Call for Industry Discussion
EnviroCheck is inviting New Zealand laboratories, environmental testing companies, assessors and industry organisations to review whether current sample-submission procedures provide enough information about surface condition and intentional subsurface sampling.
"This does not require complicated technology," Sheppard said. "It requires good field practice, good documentation and communication between the person collecting the sample and the laboratory analysing it."
"Our position is simple: know what surface you are sampling, record what happened during collection, and make sure that information follows the sample all the way to the laboratory report."
Read the Full Guide
The complete technical guide — including the field-to-report process, what EnviroCheck documents at every location, and a sampling FAQ — is available online.
Read the Sampling Technique GuideAbout Envirocheck Forensics
Envirocheck Forensics provides methamphetamine contamination assessment and property-risk services across New Zealand. The company has been involved in the development and implementation of methamphetamine surface-testing practices in New Zealand for more than a decade and continues to advocate for improved field sampling, documentation and contamination-prevention practices.
Media and Laboratory Enquiries
Todd Sheppard
Envirocheck Forensics
Email: press@MethShield.co.nz
Website: envirocheck.co.nz
This press release is provided for general informational purposes only and does not constitute professional advice, testing, or a recommendation about any specific property.