Asbestos Information, Regulations, Free Downloads, Support, Interpretation, Training Materials and

Asbestos Information, Regulations, Free Downloads, Support, Interpretation, Training Materials and more from Environmental Health & Safety Online

What is it?

Asbestos is a naturally occurring group of minerals that can only be identified under a microscope. There are several types of these flexible, fire-resistant fibers.

The word asbestos is derived from a Greek adjective meaning inextinguishable. The miracle mineral as it was referred to by the Greeks, was admired for its soft and pliant properties as well as its ability to withstand heat. Asbestos was spun and woven into cloth in the same manner as cotton. It was also utilized for wicks in sacred lamps. Romans likewise recognized the properties of asbestos and it is thought that they cleaned asbestos tablecloths by throwing them into the flames of a fire.

From the time of the Greeks and Romans in the first century until its reemergence in — the eighteenth century, asbestos received little attention or use. It was not available -in large amounts until extensive deposits were discovered in Canada in the nineteenth century (late 1800’s). Following this discovery, asbestos emerged as an insulating component in thermal insulation for boilers, pipes and other high temperature applications and as a reinforcement material for a variety of products.

Asbestos is a naturally occurring mineral. It is distinguished from other minerals by the fact that its crystals form long, thin fibers. Deposits of asbestos are found throughout the world. The primary sites of commercial production are: Canada, the Soviet Union and South Africa. Asbestos is also mined commercially in the United States.

Asbestos minerals are divided into two groups — serpentine and amphibole. The distinction between groups is based upon its crystalline structure — serpentine minerals have a sheet or layered structure, amphiboles have a chain-like crystal structure.

Chrysotile, the only mineral in the serpentine group, is the most commonly used type of asbestos and accounts for approximately 95% of the asbestos found in buildings in the United States. Chrysotile is commonly known as white asbestos or named for its natural color.

Five types of asbestos are found in the amphibole group. Amosite. the second most likely type to be found in buildings, is often referred to as brown asbestos. As you might assume, in its natural state amosite is brown in color.

Crocidolite. blue asbestos is also an amphibole. Crocidolite was used in high temperature insulation applications.

The remaining three types of asbestos in the amphibole group are: a nthophyllite, tremolite, and actinolite. These are extremely rare and of little commercial value. Occasionally they are found as contaminants in asbestos containing materials.

Once extracted from the earth, asbestos containing rock is crushed, milled (ground and graded. This produces long, thread-like fibers of material. What actually appears as a fiber is an agglomeration of hundreds or thousands of fibers, each of which can be divided even further into microscopic fibrils.

In the past, asbestos was added to a variety of products to strengthen them and provide heat insulation and fire resistance. In most products, asbestos is combined with a binding material so that it is not readily released into the air.

However, if asbestos should become airborne and is inhaled, it can remain in the lungs for a long period of time, producing the risk for severe health problems that do not appear until many years later.

Where is it found?

Asbestos Information, Regulations, Free Downloads, Support, Interpretation, Training Materials and

More that 3,000 products in use today contain asbestos. Most of these are materials used in heat and acoustic insulation, fire proofing, and roofing and flooring. Collectively, produts with asbestos in them are frequently referred to as asbestos-containing material (ACM). Asbestos gained wide spread use because it is plentiful, readily available and low in cost. Because of its unique properties — fire resistant, high tensile strength, poor heat and electric conductor, and generally impervious to chemical attacks, asbestos proved well-suited for many uses in the construction trades.

One of the most common uses for asbestos is as a fireproofing material. It was sprayed on steel beams, columns and decking that were used in construction of multi-storied buildings. This application prevented these structural members from warping or collapsing in the event of fire. Chrysotile was the most commonly used asbestos constituent in sprayed-on fireproofing. Asbestos comprised 5 — 95 percent of the fireproofing mixture and was used in conjunction with materials such as vermiculite, sand, cellulose fibers, gypsum and a binder such as calcium carbonate. These materials are soft and may be fluffy in appearance and to the touch. They vary in color from white to dark gray, occasionally they have been painted or encapsulated with a clear or colored sealant. The material may be exposed or concealed behind a suspended ceiling. Application to structural members (beams and columns) often resulted in some material being sprayed on walls and ceilings as well. This is referred to as overspray.

Asbestos is added to a variety of building materials to enhance strength. It is found in concrete and concrete-like products. Asbestos-containing cement products generally contain Portland cement, aggregate, and chrysotile fibers. The asbestos content may vary up to 50 percent by weight depending on the use of the product. Asbestos cement products are used as siding and roofing shingles; as wallboard; as corrugated and flat sheets for roofing, cladding, and partitions; and as pipes. Asbestos has also been added to asphalt, vinyl and other materials to make products like roofing felts, exterior siding, floor tile, joint compounds and adhesives.

Fibers in asbestos cement, asphalt and vinyl are usually firmly bound in the cement and will be released only if the material is mechanically damaged, for example by drilling, cutting, or sanding. Roofing shingles and siding may also show slow deterioration due to weathering.

As an insulator, asbestos received wide spread use for thermal insulation and condensation control. It was usually spray applied, trowel applied, or factory installed on or within equipment.

Asbestos proved valuable as a component of acoustical plaster. The material was applied by trowel or by spraying on ceilings and sometimes walls. It varies in color from white to gray — rarely was it painted as a noticeable loss of acoustical value occurs. Similarly as a decorative product, asbestos was mixed with other materials and sprayed on ceilings and walls to produce a soft, textured appearance.

Some of the more common products that may contain asbestos include:

Pipe and duct insulation.

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