|Heavy-Duty Diesel Fine Particulate Matter Emissions: Development and Application of On-Road Measurement Capabilities (EPA/600/R-01/079) October 2001
EPA's On-Road Diesel Emissions Characterization Facility, which has been collecting real-world gaseous emissions data since 1995, has undergone extensive modifications to enhance the facility's particulate matter (PM) measurement capabilities, with specific emphasis on fine PM or PM2.5 (particles less than 2.5 micrometers in aerodynamic diameter). At present, the facility's capabilities are focused on continuous sampling and analysis, using fast-responding instruments, such as the electrical low-pressure impactor, the tapered-element oscillating microbalance, and a particle-bound polycyclic aromatic hydrocarbon analyzer, all of which require a dilute exhaust sample.
This dilute sample has been drawn directly from the vehicle exhaust via a stack dilution system and from the ambient exhaust plume via probes in the trailer. Dilute samples have also been collected on filters for chemical and gravimetric analysis. Experimental results indicate that stack dilution sampling does not adequately represent real-world conditions as determined from initial plume sampling. Therefore, future efforts will be directed toward improved plume characterization techniques.
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