Asbestos Sample Analysis
It is often difficult to determine whether an item contains asbestos materials until it has been properly tested. As a result, the asbestos assessor will need to take several samples of suspected asbestos materials from the work site to determine their asbestos content. Taking asbestos samples is a delicate process, as it is a necessary disruption of the suspected asbestos material. In some cases obtaining a sample on your own without the assistance of a specialist is possible. However, if the material is considered “friable”—if it crumbles into smaller particles easily—contacting a professional may be the safest option.
What materials need samples?
Any materials suspected as containing asbestos require sample testing. An assessor will usually need to take a sample large enough for multiple tests, about the size of a 50¢ piece or larger. In the case of materials such as floor tiles, which are affixed to the ground, obtaining a sample may not be possible without creating a larger health risk. These materials should be marked as potentially containing asbestos and be either removed or abated.
If you are planning on obtaining an asbestos sample to send in for analysis, we recommend the following steps:
- Place plastic sheets down on the floor and over any materials near the suspected material
- Wear a P2 respirator in order to avoid inhaling possible fibres
- Wear disposable gloves
- Shut down any heating or cooling systems to avoid the possible spread of asbestos fibres
- Dampen the surface of the material first, and then cut out a full cross section.
- Place the cross section in a sealed bag, and label it for location and material type
- Seal the area where you removed the sample with duct tape or PVA glue to prevent the release of fibres.
Asbestos technicians will break up the samples and place them under a specialized polarized light microscope to determine if any fibrous materials are present. If fibres are detected, the specialist will then conduct a series of tests to determine the type of asbestos—most commonly chrysotile, amosite, or crocidolite—and the concentration of the fibres in the material.
Then conducting audits of properties, the asbestos assessor may consider that a particular item of material may contain asbestos. It can be assumed that the material does contain asbestos, or a sample can be taken to prove if in fact it does contain asbestos.
The only conclusive method of proving that asbestos is present in material is to analyse the material under a microscope.
The analysis of bulk asbestos samples is undertaken by Polarized Light Microscopy (PLM) including dispersion staining techniques. PLM is the preferred method within industry for the analysis of bulk samples mainly due to its simplicity, low cost and detection limits.
Australian Standard AS 4964 “Method for the Qualitative Identification of Asbestos” is the method most NATA accredited laboratories follow when undertaking analysis of bulk samples for asbestos. This method does not allow for a quantification estimation of the amount of fibre present within samples. The method is restricted to the identification of Chrysotile (white) asbestos, Amosite (brown) asbestos and Crocidolite (blue) asbestos only. It does not cover the identification of Tremolite, Actinolite and Anthophyllite asbestos as these asbestos types show a wide range of optical properties that cannot be equivocally identified by PLM and dispersion staining.
The method of analysis involves an initial examination of the fibres under a stereo microscope to observe and record the presence of fibre types. The fibres observed are categorized on the basis of morphology and certain physical properties. The fibres are mounted in a Refractive Index (RI) oil most closely matching the RI of the likely asbestos type. Each fibre type is then positively identified on the basis of matching the optical properties of the sample fibre against the theoretical optical properties of the different asbestos types.
Unequivocal identification of asbestos types includes the use of Dispersion Staining to obtain positive confirmation of the RIs for each asbestos type detected, agreement of appropriate and basic morphological features of the observed fibres and at least 2 and preferably 3 of the optical properties (Pleochroism, Optical Orientation, Optical Orientation) with the theoretical optical properties of standard asbestos fibre types.