Where is asbestos found?

Building materials containing asbestos were widely used from 1930 to around 1980,
particularly from the 1960s onwards. So houses and flats built or refurbished at this time may
contain asbestos materials.
Asbestos has also been used in some heat-resistant household products, such as oven
gloves and ironing boards. The use of asbestos in these products decreased greatly around
the mid-1980s, and since 1993 the use of asbestos in most products has been banned.
It is not always easy to tell whether a product contains asbestos as modern asbestos-free
materials often look similar - remember it is usually older products that contain asbestos.
Loft or cavity wall insulation does not contain asbestos.
The types of asbestos materials that may be found in homes are described below:

• Insulating board
  (Asbestos content 20-45 percent.)
  Insulating board has been used for fire protection, heat and sound insulation. It is
  particularly common in 1960s and 1970s system-built housing and is found in
  materials such as ducts, infill panels, ceiling tiles, wall lining, bath panels and
  partitions. It is unlikely to be found in buildings constructed after 1982.
• Asbestos lagging
  (Asbestos content 55-100 percent.)
  Asbestos lagging has been used for thermal insulation of pipes and boilers. It was
  widely used in public buildings and system-built flats during the 1960s to early 1970s
  in areas such as boiler houses and heating plants.
  Asbestos lagging is very rarely found in homes, especially those constructed after the
  mid 1970s. The use of asbestos for thermal insulation was banned in 1986.
• Sprayed coating
  (Asbestos content up to 85 percent.)
  Sprayed asbestos coatings were used for fire protection of structural steel and are
  commonly found in system-built flats built during the 1960s. The coatings were mainly
  applied around the core of the building such as service ducts, lift shafts, etc.
  Use stopped in 1974 and the spraying of asbestos has been prohibited since 1986.
  Sprayed asbestos has since been removed from many buildings, or sealed to prevent
  fibres being released.
• Asbestos-cement products
  (Asbestos content mainly 10-15 percent, but sometimes up to 40 percent.)
  Asbestos-cement is the most widely used asbestos material. It is found in many types
  of building as profiled sheets for roofing and wall-cladding, in flat sheets and partition
  boards for linings to walls and ceilings, in bath panels, soffit boards, fire surrounds,
  flue pipes, cold water tanks and as roofing tiles and slates. It has been commonly
  used as roofing and cladding for garages and sheds and also in guttering and
  drainpipes.
  Use has declined since 1976, but asbestos cement is still being used, particularly in
  roofing and cladding products. Asbestos cement products are unlikely to release high
  levels of fibres because of the way they are made, unless they are subject to extreme
  abrasion. Damage from weathering may also release a small amount of fibres.
• Other building materials and products
  Asbestos has been used in a variety of other building materials, for example in
  decorative coatings such as textured paints and plasters. These are still widely in
  place but supply and application has been prohibited since 1988. Plastic floor tiles,
  cushion flooring, roofing felts, tapes, ropes, felts and blankets can also contain
  asbestos.
• Heating appliances and domestic equipment
  Asbestos was used in some warm air heating systems, electric storage heaters (up to
  1976), in flameless catalytic gas heaters (up to 1988) and some early ‘coal effect’ gas
  fires.
  It has also been used in domestic equipment, such as oven gloves, ironing boards,
  seals on cooker doors and fire blankets, and in brake linings and pads.

Most respirable asbestos fibers are invisible to the unaided human eye because their size is about 3.0-20.0 µm in length and can be as thin as 0.01 µm. Human hair ranges in size from 17 to 181 µm.Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by the polymeric molecules lining up parallel with each other and forming oriented crystal lattices. These crystals thus have three cleavage planes, just as other minerals and gemstones have. But in their case, there are two cleavage planes that are much weaker than the third direction. Thus, when sufficient force is applied, they tend to break along their weakest directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring over and over until they have been broken down to their smallest unit dimensions. For this reason, one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers in a normal environment over the course of time.

As they get smaller and lighter, they become more mobile and more easily entrained (wafted) into the air, where human respiratory exposures typically result. The released fibers being heavier than air will eventually settle in quiescent conditions only to be resuspended over and over again by any kind of activity or air currents over a period of time. This cyclic re-entrainment has consequences. Consistent with the tenets of the Second Law of Thermodynamics, the smallest sizes of easily mobile asbestos fibers move away from their initial source location in an ever-broadening manner. They disperse both by simple spontaneous airborne diffusion and through mass transport of the fibers. This latter is an energy-driven process that can occur through directed air currents or by "pickup and release" along a pathway of directed movement by persons, mechanical equipment or vehicles.

For these reasons, asbestos is not an even source of contamination and thus does not tend to remain localized at its initial release point but will eventually spread throughout all available accessible areas of buildings, even into areas that don't have their own asbestos-containing products. Eventually asbestos from virtually all products that were manufactured from this mineral will invade each and every space within an affected building. This is because during the lifecycle of each asbestos product, microscopic fibers and larger particles or pieces of these products are typically produced during their residency. The lifecycle of an asbestos containing product begins from the initial delivery of the product to the building, followed by its installation, normal usage forces, age-related deterioration, physical or chemical damage that often occurs, to finally its removal either for replacement or demolition. Any small impact or damage to a typical asbestos containing product can easily release billions to trillions of fibers of asbestos into the immediate environment which then add to the pool of similar fibers and particles from other asbestos containing products within that building.

Friability of an asbestos containing product means that it is so soft and weak in structure that it can be broken with simple finger crushing pressure. Friable materials are of the most initial concern due to their ease of damage. But non-friable asbestos containing materials are not necessarily safe. The forces or conditions of usage that come into intimate contact with most non-friable asbestos containing materials are substantially higher than finger pressure. Because of this, non-friable asbestos products can and do release substantial quantities of free asbestos fibers into their environments as well. During normal usage, initially non-friable products slowly change into a quasi-friable condition. Asphalt asbestos floor tiles are typically worn down through a sanding action of the normal floor grit under foot traffic on such floor coverings. Asbestos shingles, siding and roofing materials are eroded through drying, weathering, embrittlement, acid rain leaching and other deteriorative changes to their binder matrix resulting in release of asbestos fibers ("chalk dust") when simple contact is made with their surface or when the wind blows across them. Most government regulations treat such products with much less care than they do when addressing more friable products.