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Asbestos

- a generic term for a group of minerals found in veins in rock consisting of textile like silicate fibres. The most common members of this group are chrysotile, crocidolite and amosite. Chrysotile also known as white asbestos is the most widely used and its fibres are soft, flexible and curly. Crocidolite is better known as blue asbestos and has very strong needle like fibres, while amosite, brown asbestos, has harder spikey fibres.

Capable of being woven, asbestos has been used by man for a variety of purposes for over 4,000 years. Separated out, the fibres are an excellent heat insulant or fire retardant and were widely used for this purpose from the early 19th to the later 20th century, often being sprayed on. It was also used as floor deafening and during the early to mid 1900s as reinforcement in concrete and fire proof materials such as corrugated sheeting, wallboard etc and even, a ghastly asbestos roofing slate. Health risks from airborne fibres were known about in the mining industry from the later 1800s and the building industry, where damaged products can generate fibres, eventually caught on in the mid 1900s when, in 1969 its use was regulated. In the UK, blue and brown asbestos was banned in 1985 and white asbestos in 1999, which was fairly typical of the sequence of events in most countries.

Asbestos where it is known to exist in a building has to be removed or if left in situ made safe, both of which are specialist operations which can add considerably to the cost of building refurbishment. The process emphasises the need for thorough, detailed survey of any building prior to work commencing. If asbestos is found after work has started, not only can it be expensive to remove, it can cause significant delay.