NIOSH 7500 – Product & Materials Guide

Free Crystalline Silica Concentration by XRD

NIOSH 7500 is a detailed method used to measure exposure to respirable crystalline silica (RCS) in the workplace. Respirable crystalline silica can be defined as crystalline silica particles with a diameter less than 10 microns (μm). Similar to OSHA 142, NIOSH 7500 can distinguish concentrations of all three polymorphs of crystalline silica (i.e., quartz, cristobalite, tridymite) within collected samples. While quartz is the most common polymorph, newly published exposure limits from OSHA and the EU are based upon all three polymorphic forms.

NIOSH 7500 testing samples are collected using a 37 mm, 5.0 μm PVC membrane in a two-piece cassette filter holder, a 10 mm cyclone, and a personal sampling pump. Placing a cyclone between the cassette and sampling pump when sampling at the recommended rate prevents non-respirable particles (>10 μm) from being collected in the cassette. After collection, samples are processed and transferred to a 0.45 μm silver membrane for diffraction analysis via XRD. Prior to sample analysis, calibration curves are generated with quartz, cristobalite, and tridymite standards of varying concentrations.

Analytical Method: XRD (x-ray diffraction)

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Materials needed for NIOSH 7500

  • 37 mm, 5.0 μm PVC membrane supported with backup pad in a two-piece cassette filter holder
  • Tape or a cellulose shrink band
  • 37 mm, 5.0 μm PVC membrane in three-piece cassette filter holder
  • High-volume pump (3L/min)
  • 25 mm, 0.45 μm silver membrane
  • Forceps to handle filter membrane

Products for NIOSH 7500

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