Asbestos PCM (Phase Contrast Microscopy) samples use a light microscope to see fibers. The microscope can be hand carried. One of the advantages of this method is mobility. Samples can even be analyzed on-site, which decreases the turnaround time. The microscope magnifies objects approximately 400 times their actual size.
The main disadvantage of the Phase Contrast Microscopy methodology is that it is not asbestos specific.
The analyst counts any fiber that falls into a field of view that is greater than or equal to 5 μm in length, with a 3:1 aspect ratio(three times longer than its width).
You need to be aware of this when requesting that we use this type of sample analysis there are limitations. Items such as carpets, wood, fiberglass, and drywall can produce fibers that fall in this size range and will be counted along with asbestos fibers in determining exposure.
See the EPA’s List of PACM (Presumed Asbestos Containing Materials).