For environmental samples, one must normally resort to electron microscopy for positive identification. However today gravimetric and PCM/PLM techniques are employed, which cannot readily identify the smallest, most hazardous, fibers. These techniques being limited to PM10 particulate size evaluation which completely ignores UFPs.

Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its resistance to heat, electrical and chemical damage, sound absorption and tensile strength. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. Asbestos was used in some products for its heat resistance, and in the past was used on electric oven and hotplate wiring for its electrical insulation at elevated temperature, and in buildings for its flame-retardant and insulating properties, tensile strength, flexibility, and resistance to chemicals.

Types and associated fibres

Six minerals are defined as "asbestos" including: chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite.

White

Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks which are common throughout the world. Serpentine rock is also the state rock of California. Its idealized chemical formula is Mg₃(Si₂O₅)(OH)₄. Chrysotile fibers are curly as opposed to fibers from amosite, crocidolite, tremolite, actinolite, and anthophyllite which are needlelike. Chrysotile, along with other types of asbestos, has been banned in dozens of countries and is only allowed in the United States and Europe in very limited circumstances. Chrysotile has been used more than any other type and accounts for about 95% of the asbestos found in buildings in America. Applications where chrysotile might be used include the use of joint compound. It is more flexible than amphibole types of asbestos; it can be spun and woven into fabric. The most common use is within corrugated asbestos cement roof sheets typically used for outbuildings, warehouses and garages. It is also found as flat sheets used for ceilings and sometimes for walls and floors. Numerous other items have been made containing chrysotile including brake linings, cloth behind fuses (for fire protection), pipe insulation, floor tiles, and rope seals for boilers.

Brown