Asbestos FAQ

Asbestos is a name given to a group of naturally occurring minerals contained within rocks first mined circa 1878.

Asbestos can be sub-divided into two groups:

Serpentines and Amphiboles

There are six types of asbestos although only three are common and widespread.

Chrysotile

common name - White asbestos (Serpentine)

Amosite

common name - Brown asbestos (Amphibole)

Crocidolite

common name - Blue asbestos (Amphibole)

The colours used in their common names relate to the freshly mined colour and cannot be used for identification purposes due to changes that occur as a result of ageing and production, some less scrupulous manufacturers have been known to dye white asbestos blue, as it was a superior grade and therefore commanded a better price.

Asbestos also contains traces of other minerals; iron, gold, talc and vermiculite. All types, no matter where found, have the unique structural ability to divide many times into fibres which are soft to the touch yet strong to certain planes. They are virtually indestructible, both mechanically and chemically and yet can be moulded into slurries which dry to form rigid asbestos based materials.

Asbestos was known as the magic mineral because of its strength, resilience, inertness and flexibility.

Its properties are considered under the following headings:

Chemical

Used as heat and flame retardants, it will break down at around 600 degrees centigrade, the reason asbestos was used for fire protection is that it did not have a melting point, therefore its decomposition may lead to bi-products fusing at temperatures over 1000 degrees centigrade.

Physical

The tensile strength of asbestos in constructional use is exceeded only by that of carbon fibre, and consequently it is the key physical property, also of importance is its resilience, which makes its use in the friction industry invaluable; notably to manufacture brake and clutch linings.

Thermal

Because of its poor thermal conductivity both internal and between fibres, it made an excellent material for Thermal Insulation (Lagging).

Asbestos was extensively used in the building industry and can be divided into the following:

1: Asbestos cement products - Water Absorption <30%

A mixture of white asbestos and a non combustible fill such as Portland cement (hence the name asbestos cement). The mixture was compressed with water into the required shape and left to set for up to 2 weeks using high compression presses, leading to its high density and hard surface.

Found as:

• Corrugated roofing sheets, cappings, ridge tiles, roof tiles
• Rainwater goods, soil pipes, flue pipes
• Water tanks

2: Asbestos Insulation Boarding (AIB) Water Absorption >30%

A product similar to the hard surfaced asbestos sheets, sometimes difficult to tell them apart, but it has a higher asbestos content up to 50% more often Amosite ( Brown ) asbestos with small amount of Chrysotile (white) asbestos, manufactured in a similar manner to cement but with low compression and consequently a density reduction which makes it more fibrous.

Typically found as:

• Boarding used to manufacture partitions
• False ceilings
• Inner cladding to walls and roofs in factorie
• Fire protection to support steel work
• Fire protection to doors

In the domestic market AIB may be found in the form of:

• Bath panels
• Panels behind sinks and toilet cisterns
• Used to construct ducts / voids where pipes are boxed in
• To line out airing cupboards
• Behind gas & electric fires
• Fixed to doors and loft hatches as fire protection
• External soffits and fascias

3: Asbestos Millboard, Insulation & Coatings

Millboard

Contains Chrysotile (White) asbestos 45-98% combined with fillers which exhibit greater non-combustibility than Portland cement, it provides a higher level of thermal insulation used in ovens, cylinder head gaskets, asbestos paper used to line the underside of industrial roofs.

Insulation (often referred to as "lagging")

A mixture of any or combined asbestiforms mixed with silica or magnesia cement used as it suggests to insulate pipes, boilers, furnaces, turbines etc. not widely used in the domestic market but has been found in larger properties or as a result of laggers giving friends a hand - or in multi storey properties where services may be insulated in common risers, voids or ducts.

Sprayed Coatings

The process consisted of applying, with a spray gun, hydrated asbestos normally around 60-90% asbestos content, to awkward uneven surfaces such as support steelwork in industrial buildings, offices, hospitals and the like for fire protection, on turbines in power stations for thermal insulation, wall and ceilings in churches, theatres, swimming baths for acoustic properties.

Artex and asbestos containing paints

Defined within the regulations as a coating the addition of up to 5% asbestos (usually white) into the paint/mixture was to provide a textured finish, this also improved strength, cohesion and improved the covering capacity of the paint.

For example Artex has changed from a dry powder containing 4/5% asbestos to one, which with the addition of an emulsion binder contained 2% asbestos to one which is now asbestos free known as Artex W14.

Floor Coverings

Older PVC tiles and coverings contained 5-10% white asbestos for added strength.

Joints and Packing

Gaskets, ropes, yarns used as suggested between boiler and pipe joints.

The five most significant are:

• The Health & Safety at Work Act 1974
• The Control of Asbestos Regulations 2006
• Work with asbestos Containing Materials Approved Code of Practice for The Control of Asbestos Regulations 2006 (L143)
• Asbestos : The Licensed Contractors Guide HSG 247
• Asbestos : The Analysts Guide to Sampling, Analysis & Clearance Procedures HSG 248

• For other regulations, codes of practice, guidance notes, leaflets: HSE Books
• Further information about asbestos can be found at: asbestos@wikipedia