Asbestos-Containing Materials Identification and Assessment
What to know
A material is presumed asbestos-containing (PACM) until sampling proves otherwise; the classic PACM categories are thermal system insulation (TSI) and surfacing materials (sprayed or troweled acoustical/plaster) in buildings constructed before the cutoff dates in the standard, plus resilient floor covering in some frameworks. Presumption shifts the burden: if you cannot document a negative, treat it as asbestos.
Bulk sampling must be done by a qualified person, in a way that represents the material, and analyzed by an accredited laboratory using polarized light microscopy (PLM) with dispersion staining; point counting and gravimetric/mill methods may be needed for fine or layered materials. The key concept is that a single grab sample from a homogeneous area is not enough; multiple samples per homogeneous area are required, and "homogeneous" means uniform in color and texture.
Assessment also covers condition (friability, damage, water damage) and accessibility. Friable means hand pressure crumbles it; damaged friable material is the priority. Disturbance potential matters as much as percent asbestos: a 1% chrysotile pipe wrap that crumbles is a bigger problem than an intact 50% floor tile.
Traps
Watch for questions implying PLM identifies every fiber with certainty, that percent asbestos alone determines hazard, or that intact material needs no O&M plan. Also beware claims that a pre-cutoff building's TSI can be assumed non-asbestos without records.
Rule of thumb
Presume until proven: if the building predates the cutoff and no accredited lab report exists for that homogeneous area, treat the material as ACM and control the disturbance.