Monitoring Motor Vehicle PM Emissions: An Evaluation of Three Portable Low-Cost Aerosol Instruments

The burgeoning diversification of particulate matter (PM) emissions regulations creates the need for aerosol monitors for use in engine development, on-board PM measurement, off-road emissions testing, roadside monitoring, and other applications where conventional instruments are impractical or too costly. This work critically examines from two perspectives the performance of three small, relatively inexpensive devices, the DustTrak, Pegasor Particle Sensor, and Diffusion Size Classifier, in engine exhaust PM measurement. First, results from chassis dynamometer vehicle emissions testing reveal that all three can provide accurate PM data that correlate well with the regulatory methods for PM mass and number, but only when there is little variation in morphology and composition. Second, detailed laboratory characterizations with oil and soot aerosols are reported that elucidate how these devices respond to particle size, morphology, and composition. They show that changes in aerosol properties affect all three monitors, but to a degree that depends on their particular detection method, optical, electrical charging, and charging plus diffusion. The results provide calibration data and describe conditions under which these monitors can reliably record PM emissions from engine exhaust.