What is a Composite Meth Test? Lab vs Field Composite Testing.
What is a Composite Meth Test?
When a property is tested for methamphetamine (meth or “P”), samples are taken from selected surfaces using a 10 cm × 10 cm area. Each individual sample is known as a discrete sample.
A discrete sample can be analysed individually, or several samples can be combined and analysed together as a composite sample.
Composite testing is commonly used as an initial screening method because it allows several areas of a property to be tested at a lower cost than analysing every sample individually.
There are two main types of composite meth testing: Lab Composite Testing and Field Composite Testing.
MethTec uses Lab Composite Testing for our Screen Tests.
Field composite tests have been banned under the new rental regulations but are still allowed under the NZ Standard.
What is Lab Composite Test
For a Lab Composite Test, MethTec takes individual samples from selected areas throughout the property.
Each sample is separately collected, labelled and recorded so there is a clear record of where it was taken. The individual samples are then sent to the laboratory, where they are combined for analysis.
The laboratory provides a numerical result, rather than simply a positive or negative result.
If methamphetamine is not detected, the report will show a result below the laboratory's reporting limit.
If methamphetamine is detected, the composite result confirms that meth is present in at least one of the areas sampled. However, because the samples have been analysed together, the composite result does not tell us which individual room or surface is responsible for the result.
What happens if the Composite Test is positive?
A positive Composite Test means methamphetamine has been detected, but it does not necessarily mean that every room sampled is contaminated at the level shown on the composite result.
Where further investigation is required, Detailed Testing is carried out. Individual samples are taken and analysed separately to establish where the contamination is located and the level present in each area.
This information can then be used to determine whether cleaning or decontamination is required and what areas of the property need attention.
The applicable level will depend on the type of property and the circumstances, so MethTec will explain the results and the appropriate next steps.
What is a Field Composite Test?
A Field Composite Test is different.
With a Field Composite Test, samples from several areas are combined at the property into a single sample container before being sent to the laboratory.
The laboratory therefore receives one combined sample rather than separately identifiable samples from each location.
If methamphetamine is detected, the result confirms that meth is present somewhere within the areas sampled, but it does not identify which individual location produced the result.
Why does MethTec use Lab Composite Testing?
MethTec does not offer Field Composite Testing as our standard screening method.
We prefer Lab Composite Testing because the samples are individually collected, labelled and documented before being sent to the laboratory. This provides a clearer record of exactly where sampling was undertaken.
It is an effective and economical way to initially screen a property for methamphetamine contamination.
If the Screen Test detects methamphetamine at a level requiring further investigation, MethTec can then advise whether Detailed Testing is required to determine the location and extent of the contamination.
Lab Composite vs Field Composite
Lab Composite | Field Composite |
Samples collected individually | Samples combined at the property |
Each sampling location separately recorded | Several locations make up one combined sample |
Samples combined by the laboratory | Samples combined by the tester |
Provides a numerical composite result | Provides a combined composite result |
Used by MethTec for Screen Testing | Not offered by MethTec as our standard Screen Test |
In simple terms: a Composite Meth Test is a cost-effective way of screening several areas of a property to determine whether methamphetamine is present. If an elevated result is found, Detailed Testing may then be required to establish exactly where the contamination is and at what level.
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