ASTM 7200

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)

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