A comparative analysis of temporary and permanent beta attenuation monitors: The importance of understanding data and equipment limitations when creating PM2.5 air quality health advisories

Mobile particulate monitors are being widely used for smoke monitoring throughout the western United States. While this provides valuable additional data for public health decisions, quantifying the field performance of this equipment is necessary to understand measurement limitations when being compared with federal compliance instruments. Met One Instruments, Inc. Environmental Beta Attenuation Monitors (EBAMs) were co-located at permanently established Beta Attenuation Monitor (BAM) sites to determine agreement under normal field operating conditions. Monitors were assessed for agreement between fine particulate matter (PM2.5) measurements. The instruments correlated for hourly (R2 0.70) and daily (R2 0.90) means. Mean difference for EBAM to BAM comparison showed the EBAM over-predicting the BAM by 24% (3 μg m−3). Hourly concentrations fluctuated more in the EBAM. Daily mean concentrations were the most equitably comparable measurement for these monitors. Increases in relative humidity (RH) were associated with increased disagreement between monitors. When EBAM internal RH was below 40%, R2 increased (0.76 hourly, 0.93 daily). The EBAM produced higher hourly AQI estimates. As a result of this study, it is advised to invalidate hourly data when the internal RH is greater than 40% and to only use daily AQI estimates to limit the EBAM AQI over-prediction.