| Abstract | Mass-concentration aerosol instruments require frequent calibration to provide precise and accurate measurements. Such calibrations for mass instruments can be achieved with the Centrifugal Particle Mass Analyzer (CPMA)–Electrometer Reference Mass Standard (CERMS). This study presents an interlaboratory comparison of CERMS and its two major components: the Faraday Cup Aerosol Electrometer (FCAE) and CPMA. The CERMS repeatability and reproducibility, defined as measurement precision under repeatable and reproducible measurement conditions, are evaluated. Our study was conducted in two phases: laboratory and field studies, and involved three independent laboratories. In the laboratory study, comparisons were made using soot and size-selected dioctyl sebacate (DOS) particles, using a transfer instrument. In the field, nebulized ammonium sulfate and soot from two turbine engine source exhausts, including a J85 turbojet engine, were used to compare the CERMS systems using three transfer instruments. Results indicated that the FCAEs exhibited excellent repeatability and reproducibility (<2%), while the CPMAs showed excellent repeatability (<3%) but poorer reproducibility (about 10%) due to instrument biases. In the laboratory study, the entire CERMS system demonstrated low uncertainty under repeatable conditions (3%) but higher uncertainty under reproducible conditions (∼11%). Field study uncertainties for CERMS were larger than in the laboratory (repeatability ∼8%, reproducibility ∼11%), likely due to the combined uncertainties from the transfer instruments, particle sources, CERMS components, and the less-controlled environment. Since biases between CPMAs were the major contributor to overall CERMS reproducibility, CPMA calibration could provide a significant improvement to CERMS reproducibility. |
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