NIOSH 7400– Product & Materials Guide

Asbestos and Other Fibers by Phase Contrast Microscopy

NIOSH 7400 provides two counting methods and acceptable exposure limits for airborne asbestos and other fibers but cannot be used for fiber identification. Samples are collected using a 25 mm air monitoring cassette equipped with a 50 mm electrically-conductive cowl and a MCE membrane filter. The sampling flow rate should be at least 0.5L/min, but sampling time should be adjusted to obtain optimal fiber density (100 to 1300 fibers/mm2). After collection, samples are processed to collapse the filter, creating a non-grainy background for easier fiber counting by phase contrast microscopy. Fibers with a diameter <0.25 µm will not be detected by this method. Alternate counting rules in this method may also be used to count fibers for other materials, such as fibrous glass. Our product portfolio contains all the Millipore® filtration products you need for particle monitoring, regardless of your method or application.

Analytical Method: Visual, phase contrast microscopy

Learn more about the NIOSH 7400 method

Materials needed for NIOSH 7400

  • 25 mm MCE membrane with pore size between 0.45 - 1.2 µm
  • 25 mm cassette with 50 mm conductive cowl
  • Forceps to handle filter membrane

Products for NIOSH 7400

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