Abstract Number: 617 Working Group: Instrumentation and Methods
Abstract JQA has been providing the service for calibrating the particle-counting efficiency and size classification threshold of the light-scattering airborne particle counters (LPCs). The calibrated counting efficiencies are traceable to Japan’s national primary measurement standard for the aerosol particle number concentration. The current upper size limit of the service is 0.2 µm which corresponds to the upper size limit of the national primary standard. However, there are a number of LPCs whose detectable size range is beyond 0.3 µm; therefore, there is a need for extending the calibration size range toward larger sizes. In this study, the counting efficiency of LPCs and their uncertainties were evaluated. The polystyrene latex spheres (PSL) at 0.2, 0.3, 0.5, and 0.8 um were used as the challenge aerosol. The mobility-classified PSL particles were dispersed in a 2 L cylindrical metal chamber which has twelve sampling ports at its bottom end. Two types of LPCs (RION KC-22A and KC-22B) were calibrated simultaneously using a condensation particle counter as a reference instrument. The sampling flowrates of KC-22A and 22B are 2.83 L/min and 0.3 L/min, respectively. The matrix of the measured counting efficiencies has five dimensions: two LPCs, four particle diameters, six combinations of sampling ports, five repeated measurements within a day, and four days of identical experiments. The matrix was used as the input of the analysis of variance (ANOVA). The size dependence of the counting efficiency between two LPCs were not statistically significant indicating that the size-dependent particle motions in our calibration system do not cause any bias in the calibration results over the size and sampling flowrate range investigated. On the other hand, the variation among different days was statistically significant suggesting such effect needs to be accounted in the uncertainty budget of the calibrated counting efficiency.