Course Description:
Recorded at AIHce EXP 2023

Presentations
Demonstration of Models to Predict Respirator Particle Capture Efficiency

The use of filtering facepiece respirators (FFRs) of various types increased dramatically by both workers and the public during the ongoing COVID-19 pandemic. This increased use has, likewise, instigated a proliferation of research on the qualities of FFRs. An aspect of FFR development and optimization involves the use of mathematical models that predict filter efficiency based on various filter characteristics while also considering a number of particle capture forces. These forces include the physical forces of diffusion, interception and impaction. However, modern FFRs contain electrostatically charged fibers and the aerosol itself can carry a charge of various magnitudes. Therefore, a complete model of filter performance must include equations that account for both fiber and particle charge. Once a complete model was developed, laboratory methods were utilized to validate the model given filter media with known qualities and relative to the measured efficiency of N95 FFRs. Various characterizations of the filter performance of an FFR were then possible with the use of the model including its efficiency while breathing and assessment of overall performance.

Co-Authors
None

Acknowledgements & References
R. Altmaier, The University of Iowa, Iowa City, IA, USA, Equipment and instrument support and education

Author
Patrick O'Shaughnessy PhD, CIH, The University of Iowa Iowa City, IA

Temperature Dependence for Generating Vapor o-Chlorobenzylidine malononitrile and the Impacts on Lab Testing and NIOSH Certification of Air Purifying Respirators

In this case study, o-chlorobenzylidine malononitrile (CS) vapor was generated at various temperatures ranging from 25 °C to 45 °C. This study was a result of attempting to mimic the NIOSH STP-0050 method and generate a challenge concentration of 3 ppm at 25 °C. We ran into issues generating the necessary 3 ppm CS vapor while at 25 °C and a maximum concentration of 0.7 ppm CS was achieved at 25 °C. In order to generate higher CS vapor concentrations, it was necessary to increase the temperature of the set-up. A linear correlation was found between CS vapor concentration and temperature of experimental set-up. The highest CS vapor concentration we generated was 2 ppm at 45 °C. The data and knowledge from this study has implications for other cartridge testing labs and air respirator manufacturers who may want to change their approaches when performing and requesting this type of test for either research purposes or for NIOSH certification submission.

Co-Authors
C. Manning, Assay Technology, Livermore, CA, USA.

Acknowledgements & References
P. Swearengen., USA

Author
Maria Peralta, PhD, Assay Technology Livermore, CA
United States of America

Contact Hours:
1

Presentation Date:
05/24/2023

Presenters:
Karen Jones, CIH, CSP
Patrick O'Shaughnessy PhD, CIH
Maria Peralta, PhD