Sampling and Counting Airborne Fibers Including Asbestos Fibers, in Mines and Quarries, by Phase Contrast Microscopy and Transmission Electron Microscopy
- This ASTM standard is based on other PCM methods including the NIOSH 7400, OSHA ID-160 and ISO 8672.
- For the determination of the concentration of fibers/ml of air by PCM
- Fibers counted are placed into three different groups:
- Group 1: fibers showing curvature, have splayed ends or appear as bundles
- Group 2: fibers longer than 10 microns or thinner than 1 micron
- Group 3: All other countable fibers
- If the PCM concentration exceeds ½ the PEL or TLV then examine the data to determine if 50% of the countable fibers fall into group 1 and 2. If so then there is an increased chance that asbestos is present in the sample and TEM should be employed to supplement the PCM analysis.
- The method gives guidance for “differential counting” which can help to indicate whether the fibers in question are asbestiform (vs. cleavage fragments for example)