During a PCM AHERA clearance count, fibers are counted only with what characteristics?

The correct choice is based on the specific criteria established for counting fibers in a PCM (Phase Contrast Microscope) AHERA (Asbestos Hazard Emergency Response Act) clearance count. In this context, fibers are counted if they meet a length of greater than 5 microns and have a width ratio of 3:1 or more, which allows for identification of asbestos fibers specifically.

The emphasis on a length greater than 5 microns is crucial as it helps to distinguish asbestos fibers from other fibrous materials that are shorter and may not pose the same health risks. The 3:1 aspect ratio further ensures that what is counted is likely to be asbestos and not non-hazardous fibers, adding specificity and accuracy to the assessment. This standard is important in ensuring public safety and compliance with regulations regarding asbestos presence in buildings.

Understanding this definition plays a key role in the duties of a site surveillance technician, as accurate counting and reporting of asbestos fibers is critical in determining site clearance for safety.