The method is suitable for all common asbestos-containing materials and can distinguish between asbestos fibres and elongate mineral fragments or other materials in almost all situations. In the Analytical Laboratory the representative sample of the material thought to contain asbestos is examined by eye, followed by a more detailed examination using a low power (X 8 to X 40) stereo microscope.
One or more representative sub-samples are prepared mechanically and/or chemically for further examination. Fibres observed in the course of these examinations are categorised tentatively on the basis of morphology and certain physical properties.
Each fibre type is analysed by selecting a few fibres or bundles of fibres, these are mounted in a refractive index (RI) liquid chosen to match the most likely asbestos type. The fibres are then positively identified as one of the six regulated asbestos types on the basis of their detailed optical properties using polarised light microscopy (PLM) with magnifications X 80 upwards, as appropriate to the type of sample.
BDA Surveying Ltd holds a UKAS accreditation (UKAS Testing Laboratory No. 2791) for undertaking Bulk Sample Analysis.
Analysis procedures are undertaken by Analysts holding the British Institute of Occupational Hygiene P401 Proficiency Certificate and comply with the Health and Safety Executive publication HSG 248 Asbestos: The analysts guide.