A technique to measure respirator protection factors against aerosol particles in simulated workplace settings using portable instruments

Abstract

The aim of this study was to develop a new method to measure respirator protection factors for aerosol particles using portable instruments while workers conduct their normal work. The portable instruments, including a set of two handheld condensation particle counters (CPCs) and two portable aerosol mobility spectrometers (PAMSs), were evaluated with a set of two reference scanning mobility particle sizers (SMPSs). The portable instruments were mounted to a tactical load-bearing vest or backpack and worn by the test subject while conducting their simulated workplace activities. Simulated workplace protection factors (SWPFs) were measured using human subjects exposed to sodium chloride aerosols at three different steady state concentration levels: low (8x10³ particles/cm³), medium (5x10⁴ particles/cm³), and high (1x10⁵ particles/cm³). Eight subjects were required to pass a quantitative fit test before beginning a SWPF test for the respirators. Each SWPF test was performed using a protocol of five exercises for 3 min each: (1) normal breathing while standing; (2) bending at the waist; (3) a simulated laboratory-vessel cleaning motion; (4) slow walking in place; and (5) deep breathing. Two instrument sets (one portable instrument {CPC or PAMS} and one reference SMPS for each set) were used to simultaneously measure the aerosol concentrations outside and inside the respirator. The SWPF was calculated as a ratio of the outside and inside particles. Generally, the overall SWPFs measured with the handheld CPCs had a relatively good agreement with those measured with the reference SMPSs, followed by the PAMSs. Under simulated workplace activities, all handheld CPCs, PAMSs, and the reference SMPSs showed a similar GM SWPF trend, and their GM SWPFs decreased when simulated workplace movements increased. This study demonstrated that the new design of mounting two handheld CPCs in the tactical load-bearing vest or mounting one PAMS unit in the backpack permitted subjects to wear it while performing the simulated workplace activities. The CPC shows potential for measuring SWPFs based on its light weight and lack of major instrument malfunctions.

Keywords:

• Handheld CPC
• PAMS
• portable aerosol instrument
• respirator performance
• simulated workplace protection factors

Acknowledgments

This study was partially supported by the NIOSH Nanotechnology Research Center (NTRC). The authors want to thank Ms. Judi Coyne (NIOSH NPPTL, Pittsburgh, PA), Dr. Kevin H. Dunn (NIOSH DART, Cincinnati, OH), Dr. Susan Xu (NIOSH NPPTL, Pittsburgh, PA), and Ms. Caitlin M. McClain (NIOSH NPPTL, Pittsburgh, PA), for their valuable review comments for the manuscript.

Disclaimer

The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention. Mention of company names or products does not constitute endorsement by NIOSH.