Polarized Light Microscopy (PLM) is the method most often employed for the analysis of bulk building materials. The light microscopy method 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 types that compose the asbestos mineral family. Moreover, the technique records the identity of the non-asbestos fibrous component(s) of each bulk building material sampled.
PLM results are reported as a percentage for each layer of the total sample. PLM utilizes a few protocols for the quantification process. These include visual estimation and point counting. Depending on the sample matrix, PLM analytical sensitivity can be a fraction of a percent. Other techniques can be used to further enable the identification of asbestos such as point count and gravemetrical reduction.
