104 Africa. All types of asbestos occur as long fibrous crystals, which split
longitudinally i.e. along the length of the fibre to form progressively thinner fibres. The main types of asbestos are shown below:
Asbestos
Amphibole Serpentine
Crocidolite Blue Asbestos
Amosite Brown Asbestos
Anthrophyllite
Tremolite
Actinolite Chrysotile
White asbestos
Source: Adrian Hirst
The two groups of asbestos fibres have different crystalline structures and correspondingly different shapes and properties. When viewed under a
microscope, Chrysotile white asbestos fibres appear to be slightly curly, whereas, Crocidolite blue asbestos fibres are straight and shorter. Amosite
brown asbestos fibres are similar to Crocidolite but more brittle. It should be noted that colour is not a reliable means of identifying the types of asbestos,
especially when it is incorporated into a product.
11.1.2 Properties of Asbestos
The main properties, which have led to the extensive use of asbestos, include incombustibility, mechanical strength, chemical resistance, thermal insulation
105 and low cost. Various types of asbestos may exhibit these properties to
different extents, which affects their usage.
11.1.3 Uses of Asbestos
The most common applications of asbestos likely to be found on industrial premises are given in below, together with the type and approximate content
of asbestos.
Common Applications of Asbestos in Industrial Premises Product
Type of Asbestos Approximate
Content
Cement Materials e.g. corrugated sheets, water
tanks, pipes, prefabricated building components.
Chrysotile occasionally incorporating Crocidolite or
Amosite 10 - 20
Fire-resistant Insulating Board.
Amosite occasionally incorporating chrysotile or
crocidolite 15 - 40
Thermal, insulation, lagging, incl. pipe and vessel
insulation. Amosite, chrysotile
crocidolite 1 - 55
Sprayed coatings e.g. applied to structural beams
and ceilings as fire protectionandor acoustic
and thermal insulation Amosite, chrysotile
crocidolite 60 - 90
Textiles e.g. heat resistant gloves, fire-blankets, fire-
protective clothing insulation mattresses.
Chrysotile occasionally Crocidolite
85 - 100 Jointings packings
e.g. gaskets. Chrysotile occasionally
Crocidolite 25 - 85
Friction materials e.g. automotive brake clutch
lining. Chrysotile
30 - 70 Floor tiles.
Chrysotile 5 - 7
Filler Reinforcements e.g. in felts, millboards, papers,
underseals, mastics, adhesives.
Chrysotile occasionally Crocidolite for some
applications 1 - 10
Reinforced thermo-setting plastics battery cases.
Chrysotile, crocidolite amosite
5 - 20
106
11.1.4 Airborne Asbestos Fibres
The physical structure of asbestos enables it to break up into small fibres, which are capable of remaining suspended in the air for long periods. These
fibres may be inhaled and some may penetrate to, and be deposited in, the lungs.
A „countable‟ fibre is defined as a particle having a length: breadth ratio of
greater than 3:1, being less than 3 microns in diameter and greater than 5 microns in length.
11.1.5 Exposure to Asbestos Fibres
