The best source of information for asbestos and lead regulations in the State of Maine is the
Maine Department of Environmental Protection in Augusta, Maine. They can be reached by calling
(207) 287-2651. You can also reach them through their website.
Asbestos is the common name for a group of fibrous, mineral silicates, having unique properties.
These properties include:
a. Noncombustible
b. High tensile strength
c. Good noise absorption
d. Thermal insulator
e. Condensation control
f. Resistant to the effects of corrosive chemicals
g. Resistant to the effects of friction
The various types of asbestos, their characteristics, and uses are given in Table I.
B. Historical Uses
Asbestos has been used for over two thousand years. The meaning stemmed from the Greek word
"quenchable" - derived from the observation that the material would not burn.
Marco Polo reported the use of asbestos in gun powder by the Chinese.
A tablecloth belonging to Charlemagne was woven with asbestos.
In 1729, Benjamin Franklin sold a purse fabricated with asbestos to his British benefactor.
C. Modern Uses
The unique characteristics of asbestos have resulted in a very diverse use of the material over the
years. The asbestos industry reports that currently over 3,600 products contain asbestos.
Asbestos-containing products can be divided into two categories:
Category I - Friable Material and Asbestos Textile Products
Category II - Nonfriable Matrix-Bonded Composite Products
Table II lists categories, product uses, and approximate dates of use
D. Trade Names
Listed in Table III are the types of application and the associated trade names of some asbestos-containing
products
E. Methods of Application
Sprayed-On
Asbestos was sprayed onto structures in auditoriums, hallways, and classrooms for fireproofing,
noise absorption, condensation control, and decorative purposes.
Sprayed-on asbestos is usually friable.
Two methods were used to spray-apply asbestos:
Wet Method
Generally, a mixture might have consisted of a slurry of one or more of the following: asbestos (5-30%), mineral wool, and/or fiberglass, and Portland cement, gypsum, pearlite and vermiculite.
This material was more dense and less friable than that applied by the dry method (described below).
The thickness of the application usually ranged from 1/2 to 1 inch.
Chrysotile was usually used in the formulation.
The surfaces were often trowelled after application, resulting in a harder, more dense material.
Dry Method
Generally, a mixture consisted of a dry blend of asbestos fibers (5-90%) and one or
more of the following: mineral wool or fiberglass, Portland cement or gypsum, water-soluble
resins, starches, and other additives.
The mixture was applied with a sprayer and wetted as it passed through the nozzle. The
water activated the water-soluble resins, producing a wet fiber matrix, which readily adhered to
the application surface.
The thickness of the application was usually 1/2 to 2 inches.
Amosite, chrysotile, or both were often used; Crocidolite was used infrequently.
Because of the method, the asbestos content can vary greatly within the same application.
2. Pipe and Boiler Insulation
a. This insulation is usually applied by pasting preformed blocks or sheets or by applying wetted asbestos-containing
compounds.
b. Generally, three types of insulation were used:
Preformed sections, blocks or siabs
Insulating cement for values, elbows or over fiberglass ducts
Asbestos paper products (flat sheets or corrugated).
F. Airborne Asbestos
Unlike many man-made fibers, asbestos as it is mined and used in manufacturing rarely is in single-fiber form. It can continue to split into smaller and smaller fiber bundles.
The average fiber diameter ranges from 0.11 to 0.24 micrometers. However, asbestos can split into even smaller bundles,which cannot be seen with an optical microscope.
These fine fibers settle from the air very slowly. In completely still air, fibers of the size usually found in overhead spray insulation in a occupied 8' or 10' office take approximately 80 hours to settle.
Table I
Scientific Name
Characteristics
Source
Chrysotile
White asbestos; fine silky fibers; flexible and high tensile strength; accounts for over 90% of the uses of asbestos.
Canada Soviet Union
Amosite
Brown asbestos; brittle fibers; bonds well with plastics and is used in heat insulation materials.
South Africa
Crocidolite
Blue asbestos; strongest of the asbestos fibers; brittle fibers; usually found in combination with chrysotile in pipes and sheeting; also occasionally found with amosite or chrysotile in pipe and boiler wrap; also used as decorative material.
South Africa
These three are types of asbestos most often found in construction materials and commercial products. Tremolite, actinolite, and anthophyllite are also asbestos minerals, but rarely found in building and commercial products.
