This study introduces a new method for identifying asbestos containing materials (ACM) containing a low percentage of asbestos < or = to 10%.  Currently used Polarized Light Microscopy (PLM) and Transmission Electron Microscopy (TEM) methodologies rely on area ratio estimates to determine asbestos concentrations and have limitations at low asbestos levels.        

     The ``Internal Standard Addition" (ISA) method is designed to reduce this deficiency.  Specifically, a small portion of samle is weighed and to it is added an amount of asbestos different in type to that present in the sample and equal in quantity to a ``density adjusted 1% by weight".  The asbestos containing material (ACM) determination is made with PLM visual comparison of the two types of asbestos and if necessary, by a modified point counting technique.  Compared to the current methods, this new technique yielded a significant increase in precision and accuracy and reduction of false positives and false negatives in the range of 0.25% - 5% asbestos.