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The Wisconsin Departments of Transportation and Natural Resources evaluated the hydrocarbon (HC) detection capability of the Remote Vehicle Emissions Sensing (RVES) system, which employs remote sensing technology, and Wisconsin's I/M analyzers, which use BAR90 specifications. Both analyzers employ non-dispersive infrared (NDIR) technology. Other recent research has quantified HC measurement inaccuracies for vehicle emissions analyzers that use NDIR technology or have BAR90 specifications. This research shows that BAR90 analyzers undermeasure some water- soluble HCs and NDIR analyzers undermeasure olefinic and aromatic HCs. This evaluation was based on both field measurements and calculations that simulate these inaccuracies. These calculations give a measurement accuracy value, which estimates the fraction of the total HCs in a vehicle exhaust sample that each analyzer measures. Other calculations quantify the ozone forming potential of this measured fraction by considering the reactivity of measured HCs. Our field measurements and calculations show Wisconsin I/M analyzer HC measurements are on average 7 percent and 1 percent less than RVES, respectively. Calculations estimate that both analyzers measure at most 43 to 71 percent (an average 61 percent) of the total HCs in an emissions sample. Additional calculations estimate that the HCs measured by both analyzers have 49 to 71 percent (an average 62 percent) of the ozone forming potential of the total HCs in an emissions sample.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
