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Block Insulation

Asbestos in Block Insulation

Block insulation is rigid or semi-rigid slabs of insulating material. The insulation itself can be composed of any number of materials, including fiberglass, wool, agricultural filler, recycled rag or other substances. From the late 1850s until the early 1980s, asbestos was another common component of block insulation.

During the 19th century when most homes were lighted by gas or oil lamps and heated with wood or coal, the threat of fire was a frequent danger. In this environment, asbestos building products provided much protection against this threat. Beginning with roofing shingles, asbestos found its way into virtually all building products; asbestos block insulation was an inexpensive and popular means of making a building much more fire resistant. The most common form of asbestos used in block insulation was chrysotile, or white asbestos. Mined primarily in northwestern Montana and Vermont, this was a cheap form of fireproofing. Long-term exposure to this substance however can result in serious lung diseases such as mesothelioma cancer.

Hazards Associated with Block Insulation Products

Asbestos block insulation was installed in a large number of buildings across the United States, and many buildings are still thought to contain asbestos in one form or another. Builders who cut asbestos blocks to fit particular areas would be cutting into raw asbestos fibers and were at risk of inhaling loose airborne fibers.

Firefighters who entered burning buildings that contained asbestos block insulation were also likely to have come into contact with loose asbestos fibers, as would demolition workers or building maintenance workers. The highest level of asbestos exposure from block insulation, however, was most likely endured by those working in the factories that produced the insulation product, as they worked with the raw asbestos fibers with inadequate protective equipment.



Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)

N/A. "Asbestos Linked to Autoimmune Diseases." Environmental Health Perspectives, vol. 113 (2004)

N/A. "Block Insulation." McGraw-Hill Dictionary of Architecture and Construction. (New York: McGraw-Hill, 2003).

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