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Document Type


Organizational Units

Chemistry and Biochemistry


Atmospheric chemistry, Emissions, Pollutants


Vehicle hydrocarbon (HC) emissions can be emitted from either tailpipe or non-tailpipe locations and understanding their fleet apportionment is important for successful air pollution policy. Vehicles initially misidentified as having elevated tailpipe HC emissions first indicated that roadside exhaust sensors could detect the presence of evaporative HC emissions as increased noise in the HC/carbon dioxide (CO2) correlation measurement. The 90th percentile of the largest residual of the HC/CO2 correlation is defined as a running loss index (RLI) for each measurement. An RLI that is three standard deviations or greater above the instruments noise indicates possible evaporative running loss emissions with the probability increasing with larger RLI values. Two databases of vehicle emission measurements previously collected in West Los Angeles in 2013 and 2015 were screened using this method. The screening estimated 0.09% (31/33,806) and 0.18% (49/27,413) of the attempted measurements indicated evaporative running loss emissions from a 9-year-old fleet. California LEV I certified vehicles (1994 – 2003 model years) accounted for the largest age group for both. Minimum detection limits for the instrument used were estimated at 2.8 and 1.6 g/mile on a propane basis for the 2013 and 2015 data respectively or 32 to 56 times the Federal Tier 2 and Tier 3 standards of 0.05 g/mile.

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Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Publication Statement

This is an Accepted Manuscript for

Bishop, G. A.; DeFries, T. H.; Sidebottom, J. A.; Kemper, J. M. (2020) Vehicle Exhaust Remote Sensing Device Method to Screen Vehicles for Evaporative Running Loss Emissions, Environ. Sci. Tech. 54, 14627-14634. DOI: 10.1021/acs.est.0c05433

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