What is the pore size of the filter used in NIOSH protocol filter cassettes?

The pore size of 0.8 microns in filter cassettes used in the NIOSH protocol is specifically designed to effectively capture airborne asbestos fibers, which are typically very small and can vary in size. This size allows for a balance between capturing the majority of asbestos fibers while minimizing the loading of the filter, which can affect filter efficiency and airflow. By using a 0.8 micron filter, the protocol ensures that a significant percentage of potentially hazardous fibers are collected without significant loss of airflow through the cassette, which is essential for accurate sampling. This makes it suitable for environmental monitoring and ensuring compliance with safety standards for asbestos exposure.