Asbestos is a naturally occurring mineral found in certain rocks. It separates into strong, thin fibers that are invisible to the naked eye. Asbestos is strong, fire and corrosion resistant, and a good insulator. It was typically used in building materials as an additive to enhance strength in concrete, asphalt, roof shingles, siding, wall board, floor tiles, joint compounds and adhesives. Since Asbestos can be a great source of stability and flame control it was used in building materials before the mid-1970s and occasionally until the late 1980’s.
If the building materials mentioned above contain more than one percent asbestos as determined with polarized light microscopy (PLM) they are considered asbestos-containing materials (ACM). ACM can be friable or non-friable. Friable ACM is dry and can be crumbled or reduced to a powder by hand. Friable ACM presents greater risks to human health than non-friable ACM. When dry, non-friable ACM cannot be crumbled or reduced to a powder with hand pressure.