Many buildings contain asbestos, which was used in spray-applied flame retardant, thermal system insulation, and in a variety of other materials. Asbestos was sometimes "flocked" above false ceilings, inside technical ducts, and in many other small spaces where firefighters would have difficulty gaining access. Structural components like asbestos panels were also used. In residences, asbestos was often a component of a type of flocked acoustic ceiling called popcorn ceiling or "cottage cheese ceiling", until its production was banned in the US in 1978. However, the ban allowed installers to use up remaining stocks, so houses built as late as 1986 could still have asbestos in their acoustic ceilings. The only way to be sure is to remove a sample and have it tested by a competent laboratory.
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Depending on how and where asbestos was applied, it might not pose any risk to most users of the building. If the fibers cannot become dislodged, they cannot be inhaled, and thus the asbestos poses no risk. However, some methods of applying asbestos, particularly flocking, allow asbestos fibers to gradually drop off into the air. Asbestos poses hazards to maintenance personnel who have to drill holes in walls for installation of cables or pipes. Even if the workers are protected, such maintenance operation may release fibers into the air, which may be inhaled by others. Interventions in areas where asbestos is present often have to follow stringent procedures.
When asbestos fibers can easily be made into airborne dust, the material is known as "friable". For example, a popcorn ceiling is extremely friable, whereas asbestos floor tile is considered non-friable.
Different countries have different regulations and methods of enforcement, when it comes to asbestos removal. It is extremely important to remember that prior to any asbestos removal procedures taking place; the client has a duty of care and must verify that the specialist removal contractor can provide proof of the following:
- license if licensing is required within the jurisdiction
- specific asbestos public and employer liability insurance
- worker training to include supervisor and contract manager training within the past 12 months
- worker fit-testing and medical surveillance within 12 months
- specialist equipment testing within 6 months - DOP and PAT within the EU
Optionally, the specialist contractor should be able to provide accreditation from ARCA or other such trade organization.
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If removal is to be performed when users are still present in the building, it is usually necessary to relocate some users temporarily. Typically, the part of the building from which asbestos is being removed has to be sealed off in order to prevent contamination of the other areas. Methods of sealing off an area often include the use of polyethylene film, duct tape and negative air pressure machines which are fitted with HEPA filters. The idea is that the contained area is pulling fresh air in as to not let asbestos fibers out into the surrounding environment.
Only a special vacuum cleaner that is designed for asbestos containment (class H) can be safely used when cleaning up during and after asbestos removal. Ordinary vacuum cleaners cannot be used, even those fitted with a HEPA filter. An ordinary vacuum cleaner will expel the asbestos fibres into the room air.
If the building is closed to normal users, it may be necessary to seal it off from outside atmosphere so that no accessible air is contaminated. Examples of asbestos removal enterprises include the Jussieu Campus (begun circa 1996 and still going on as of 2005) and the Tour Montparnasse (in 2005, projected duration was three years if the tower was emptied of its users, and ten years if it were not).
An asbestos-containing building that is to be torn down may have to be sealed, and to have its asbestos safely removed before ordinary demolition can be performed. The asbestos removal may take longer and cost more than the actual demolition. For example, the former seat of parliament of East Germany, the Palast der Republik, was stripped of most of its asbestos between 1998 and 2001, before it was finally demolished starting in 2006.
New innovative methods for asbestos removal have been used as well. One example is the Lawrence Livermore National Laboratory's (LLNL) B238 building, where a track mounted wet cutting saw with a diamond blade was used in order to cut the building into small sections. These small sections were then double wrapped in plastic, the minimum requirement when transporting asbestos material, and driven to a landfill. This method not only contained the asbestos material within the gunite and metal layers of the walls, but also kept workers at a safe distance since the saw was controlled remotely.
Alternatives to removal
Removal is not the only means of asbestos abatement. Asbestos and asbestos-bearing materials may be "enclosed" or "encapsulated" to prevent building occupants from being exposed to the fibers.
Source of the article : Wikipedia