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Asbestos is the generic term for a number of naturally occurring minerals composed of fine fibres. The name is taken from the Greek word “asbestos”, which means indestructible or imperishable. The correct name for this mineral, because asbestos is resistant to acids, alkalis and high temperatures. Asbestos is strong and at the same time flexible, durable and thermically, electrically and sound insulating. In comparison to man made mineral fibres, asbestos is a cheap raw material. Asbestos is mined from rocks, whereby the rocks are comminuted. This releases the asbestos particles.

Between 1940 and 1993, a lot of asbestos was used in construction in the Netherlands. Examples are: asbestos cement, underlays for carpets, sealants, concrete glue, paints and roofing bitumen. Furthermore, it was often used for fire insulation and heat protection. In addition, asbestos was frequently used in appliances, means of transport, structures and systems (toasters, ships, cars, lorries, train carriages, roads and lift systems. Analysis There are 4 microscopic techniques that can be used to analyse a sample for the presence and concentration of asbestos:

• Stereo microscope: the stereo microscope is used for an initial visual screening of the materials suspected of containing asbestos. Using a magnification of 5 – 60 times, the material is examined for fibres that could possibly be asbestos. After identification, an estimate is made of the quantity of asbestos (m/m%)

• Polarisation microscope: A polarisation microscope can be used in many cases to determine whether a suspect fibre is indeed asbestos. For this purpose, optical properties are used, such as refraction index, double refraction, dispersion and behaviour in polarised light. A magnification is used of 100 to 500 times.

• Phase contrast microscope: fibres can be counted with the aid of a phase contrast microscope. The technique is used to count fibres on air sampling filters.

• Electron microscope: a very strong magnification of fibres can be achieved with an electron microscope (to > 25,000 times). In combination with X-ray diffraction, the elements can be determined that comprise the fibre discovered. The minerals sought are Si, Mg, Fe, Ca, Na, Mn and Al, particularly regarding their ratio, which is characteristic of a specific type of asbestos

ALcontrol Laboratories works according to the following standards:

• NEN 5707 (soil samples): if non-compacted materials are found in the fraction > 4 mm , it is mandatory to examine the smallest fraction (particles < 500 μm).

• NEN 5896 (samples of materials): reveal and identify asbestos with the aid of stereo and electron microscopy; if there is doubt, electron microscopy might possibly be used for identification.

• NEN 5897 (construction and demolition waste and rubble granulate): if non-compacted materials are found in the fraction > 4 mm, it is mandatory to examine the smallest fraction (particles < 500 μm) under an electron microscope.

ALcontrol has all the aforementioned microscopes at its disposal and is therefore able to conduct all analyses (accredited by the Raad voor Accreditatie!) fully in accordance with the relevant applicable NEN standards.