How Does Asbestos Testing Work?

How is an asbestos sample tested?

After a sample is taken of a material suspected to contain asbestos, it is then analysed by a laboratory technician. This must be done under controlled conditions and to internationally recognised and approved procedures. 

There are a range of ways that a laboratory technician will uncover the result of a sample. The method for analysis will be determined by whether the sample is for the presence or absence of asbestos, or for the level of fibres present in the air. 

But here, we are going to focus on bulk samples. 


Bulk Sample Testing

Bulk samples are generally bits or small chunks that have been severed from a larger material such as a cement board, or vinyl flooring. They determine a yes or no answer to whether asbestos is present in the material, and which types of asbestos fibres are present.

During sampling, a bulk sample must be taken with consideration to the material and the process of analysis to ensure the correct result. 

Asbestos samples should also always be double bagged before going to a laboratory for analysis to protect those who receive the sample.

For analysis for asbestos in a bulk sample, a laboratory technician’s skill is relied upon. There is currently no machine that you can stick an asbestos sample in and get a result spat out. The lab technician must apply their skills and knowledge to get that final result. 

First of all, the asbestos sample is put under a stereo microscope in a fume cabinet where it is poked and prodded to locate any fibres. The lab technician will also try to look for all the different types of asbestos within that sample. There are three main ones we commonly find in New Zealand, they are chrysotile, amosite and crocidolite.

However, what looks like asbestos to our naked eyes might not actually be asbestos. There are fibrous materials out there that look very similar to asbestos fibres even under a microscope. So, to determine whether those fibres are asbestos, they’ll then be mounted onto a slide and put under another microscope for analysis using polarized light microscopy. Asbestos is anisotropic, which means that there is a difference when is it measured along the different axes of it’s physical and mechanical properties. So the laboratory technician can utilise the different refractive indices that each type of asbestos has to determine not only that it is asbestos, but also confirm the type of asbestos.   


Limitations & Errors

There are some limitations with bulk sample analysis and there are also factors which prevent a concise result. 

Incorrect sampling technique

  • A laboratory technician needs enough of a material to find asbestos fibres. If there is not enough material in a sample bag, then the laboratory technician will only be able to look at what is there.


  • Some materials vary in how they had been applied in the first instance. For example, textured coatings also known as popcorn ceilings mostly seen in domestic houses are non-homogeneous. This means that a larger percentage of asbestos in the ceiling texture may have been applied in one corner of the room and not the others or vice versa. It is up to the person taking the sample to ensure that the sample is taken correctly. The laboratory technician can only analyse what is supplied to them.


  • Cross contamination often occurs when the tools used for sampling are not cleaned before and after taking asbestos samples. So if a material that did contain asbestos had been sampled without tools being correctly decontaminated and then a non-asbestos material is sampled afterwards, the fibres from the first material can get attached to the non-asbestos material leading to a false positive result.   

A quick hint

Taking samples is something we tend to do nearly every day, and sometimes we do it all day sample after sample. So we’re really good at it. So if you need us to come and take one for you let us know here. But if you’ve got someone else taking your sample or a lab analysing your asbestos samples try keep this in mind:

  • Look for accreditation. In New Zealand, IANZ is the best accreditation for asbestos services. Getting accreditation for asbestos laboratory analysis and getting accreditation for asbestos surveying & consultancy are different. Look for a laboratory that is accredited to the standard NZS/ISO/IEC 17025:2005. If a surveyor is taking your sample for you, make sure they are using one too. 
  • We’re an accredited inspection body, but you can check out the accredited lab we use here.  

Fibresafe NZ are a fully qualified and accredited asbestos management company based in New Zealand. We pride ourselves on our expertise in asbestos related matters, as well as our quality of service delivery. We aim to help the nation better their understanding of asbestos, and find solutions to sort their asbestos containing materials until they can be removed in a fair and pragmatic approach.

We’re proud to be accredited by IANZ, to the conformance standard ISO/IEC 17020:2012 for surveying & sampling

Find out about our services, or send us a message