Evaluation of a 25-mm disposable sampler relative to the inhalable aerosol convention

Abstract

An ideal inhalable aerosol sampler for occupational exposure monitoring would have a sampling efficiency that perfectly matches the inhalable particulate matter (IPM) criterion. Two common aerosol samplers in use worldwide are the closed-face cassette (CFC) and the Institute of Occupational Medicine (IOM) sampler. However, the CFC is known to under-sample, with near zero sampling efficiency for particles >30 µm, whereas the IOM, considered by many to be the “gold standard” in inhalable samplers, has been shown to over-sample particles >60 µm. A new sampler in development incorporates characteristics of both the CFC and the IOM. Like the CFC, it would be disposable, have a simple design, and is intended to be oriented at a 45° downward angle. Like the IOM, the new sampler has a 15-mm inlet diameter and incorporates a 25-mm filter cassette with a protruding lip. The IOM is oriented at 0° to the horizontal, so it is hypothesized that orienting the new sampler at ∼45° downward angle will reduce oversampling of larger particles. In comparison, the CFC’s inlet diameter is 4 mm; increasing the size of the inlet should allow the new sampler to have an increased efficiency relative to the CFC for all particles. A unique characteristic of the new sampler is the incorporation of a one-piece capsule-style filter that mimics the IOM’s cassette but is made of disposable material. Seven different sizes of alumina particles (mean aerodynamic diameters from 4.9–62.4 µm) were tested (total = 124 samples collected). For each test, six samplers were placed on a manikin located inside a wind tunnel operated at 0.2 m/sec. Results indicated that the new sampler improved on the CFC for smaller particles, providing a larger range for which it matches the IPM criterion, up to 44.3 µm. However, the efficiency was significantly lower in comparison to the IPM criterion for particle sizes above 60 µm. Overall, the new sampler showed promise, but additional modifications may help improve sampling efficiency for larger particles.

Keywords:

• Aerosol sampler
• closed-faced cassette
• inhalable particulate matter
• IOM sampler
• wind tunnel

Acknowledgments

The authors would like to thank Zefon International for their assistance with prototype design and manufacture. The authors would also like to thank the internal NIOSH reviewers who provided valuable comments, including Robert Streicher, Bon-Ki Ku, and James Bennett. Finally, the authors would like to thank Ms. Tracy Rees, MFA for assistance with manuscript preparation.

Disclaimer

The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention.

Additional information

Funding

This work was made possible in part by NIOSH Training Grant T42OH008414.