What the number means
µg/100 cm² means micrograms of methamphetamine per 100 square centimetres of surface, the area of a 10 cm by 10 cm square. A microgram is one millionth of a gram. So 0.5 µg/100 cm² is half a microgram across a patch the size of a coaster.
The level is a trigger, not a toxic threshold. It was set with a safety margin based on how young children are exposed: crawling, touching surfaces and putting their hands in their mouths.
How to read your results
| Result | What it means | Next step |
|---|---|---|
| Below reporting limit | No meth detected | No action |
| Below 0.5 | Acceptable for residential use | Keep the report |
| Composite near 0.5 | Average close to the level; a hotspot may be higher | Detailed assessment |
| Above 0.5 | Above the investigation level | Detailed assessment, then remediation and validation |
| Above 15 to 30 | Heavy use or possible manufacture | Consider a clan lab inspection |
How Australia compares
Countries set different levels. New Zealand's standard NZS 8510 uses a higher level for residential properties, and US states range widely, with some as low as 0.05 µg/100 cm². Australia's 0.5 sits at the protective end of the range and is the level Australian insurers, health departments and tribunals use.
Composite results need care
A composite averages several swabs. A composite of 0.4 could include one swab well above 0.5. If a composite is close to the guideline, follow it with a detailed assessment. See how meth residue testing works.
Last reviewed October 2026 by the EnviroForce team