Bulk Building Materials
The analysis of Bulk Building Materials for asbestos content is conducted by PLM, XRD, SEM and TEM. There are thousands of materials used in construction that contain asbestos. These materials include, but are not limited to pipe and boiler insulation, acoustical coatings, sprayed-on fire proofing, plasters, ceiling tiles, and floor tiles.
Polarized Light Microscopy (PLM) is the technique most often employed for the analysis of bulk building materials. The light microscopy technique utilizes the unique features of polarized light to observe mineral specific optical properties. In this manner, PLM can differentiate asbestos from non-asbestos fibers and further classify the various species that compose the asbestos mineral family. Moreover, the technique records the identity of the non-asbestos fibrous component of each bulk building material sample.
The PLM procedure provides an economical technique for screening large numbers of samples. However, as with PCM, there are limitations to light microscopy testing due to the magnification (100-400X) employed and due to other interferences present in the building material matrix (ex: tar and petroleum binding components, sub-micron particulate adhering to the surface of asbestos mineral, etc.).
PLM results are reported as a percentage of the total sample. PLM utilizes a few protocols for the quantification process. These include visual estimation and point counting. (See FAQ) Depending on the sample matrix, PLM analytical sensitivity can be a fraction of a percent. Gravimetric reduction protocols (ELAP 198.6, EPA 600 Sec. 2.3) further enhance this technique’s ability to accurately quantify and qualify asbestos.
The current method employed for these analyses is found in EPA 600/R-93/116. Other procedures are also utilized to supplement this method (ELAP 198.1). Accreditation is primarily provided by the National Institute of Standards and Technology (NIST) through the National Voluntary Laboratory Accreditation Program (NVLAP).
Extensive Quality Assurance and Quality Control (QA/QC) regimens are performed as part of an ongoing program. Proficiency testing is primarily conducted through the Proficiency Analytical Testing Program (PAT) administered by NVLAP. On-site technical evaluations are also primarily conducted through NVLAP.
Because of the limitations listed above, many regulatory bodies have recommended (some requiring) further analysis of bulk building materials by TEM(ELAP 198.4). The gravimetric reduction process usually employed on Non-Friable Organically Bound (NOB) building materials (ex: floor tiles, roofing materials, etc.) is particularly well suited for TEM confirmation of negative PLM samples. (See FAQ)