Light and Electron Microscopy EHT has sophisticated instrumentation capable of Phase Contrast Microscopy (PCM), Transmission Electron Microscopy (TEM) and Polarized Light Microscopy (PLM) testing. PCM is widely used to measure fiber concentrations of air samples and has the advantage of fast turnaround time and low cost. TEM is the standard testing procedure for most airborne investigations including post abatement clearance testing as well as diagnostic and environmental monitoring activities. PLM is used to identify asbestos and other fibers, as well as minerals and other matrix components of bulk samples such as building materials. Microscopy is also used to identify mold spores and pollen grains.