This method was developed as a Transmission Electron Microscopy (TEM) follow up to a Phase Contrast Microscopy (PCM) analysis via NIOSH 7400. Taking advantage of the TEM's ability to positively identify each fiber, the method determines the percentage of asbestos fibers versus non-asbestos fibers in the sample. This percentage is then applied to the original PCM result.
An example scenario where this method could be put to use is where it is suspected that PCM air samples are failing due to the presence of non-asbestos fibers (i.e. fiber glass).
Sample retention time - 60 days