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The development and application of qualification requirements for automotive service technicians and mechanics participating in vehicle emissions inspection and maintenance (I/M) programs is vital to the realization of maximum emissions reductions. Using the existing British Columbia (B.C.) trades qualification system for mechanics as a screening mechanism, the provincial I/M mechanic certification requirements take into account not only skill and knowledge related to automotive emissions control, but knowledge regarding the administrative requirements of the program as well. In addition to rigorous mechanic qualification requirements, the centralized B.C. Inspection program will include loaded-mode testing and NOx measurement, as well as thorough visual and functional inspection of emissions control components.

The constant volume sampling (CVS) technique, which has been part of the Federal Test Procedure (FTP) for the exhaust emissions testing of light-duty vehicles since the 1972 model year, involves the collection of a sample of exhaust gas after it has been diluted to a constant volume. The FTP specifies a formula for calculating a dilution factor (DF) that is used to correct the emission measurement for the pollutant concentration in the dilution air. Once the DF has been determined, emission measurements made using the CVS technique can be converted to a “raw,” undiluted concentration. This enables a single sampling system to be used to determine either mass emissions or tailpipe concentrations, both of which are required in certain vehicle inspection and maintenance (I/M) programs. Review of the DF calculation procedure specified in the FTP indicates that it is a simplification of a more rigorous calculation needed to most accurately determine the true DF.

The California Bureau of Automotive Repair (BAR) and Sierra Research, Inc. (Sierra) have evaluated a large number of alternative emissions test procedures and developed new procedures that could substantially increase the ability to identify defective vehicles under vehicle inspection and maintenance (I/M) programs. The primary focus of the study was to determine whether an economical “loaded mode” (dynamometer-based) test procedure could be developed that would accurately identify vehicles with emissions in excess of the applicable standards using the Federal Test Procedure (FTP). The results of the BAR/Sierra study show that, using a new “Acceleration Simulation Mode” (ASM) test, 90% of all excess oxides of nitrogen (NOx) emissions can be identified without the use of transient testing or mass emission measurement.

Evaporative hydrocarbon emissions from gasoline-powered vehicles continue to be a major concern in areas where the national ambient air quality standard for ozone is violated. As a result, accurate estimates of real-world emissions from in-use motor vehicles are of vital importance in assessing the progress made in reducing emissions, as well as in determining the need for and required magnitude of additional emissions reductions. In this study, real-world evaporative emissions testing was performed on 50 late-model vehicles (30 passenger cars and 20 light-duty trucks), ranging in age from the 1992 to 1997 model year. Six of the 50 vehicles were equipped with enhanced evaporative emission control systems. Forty-nine of the 50 vehicles were procured from an Arizona State Inspection and Maintenance (I/M) Program test lane located in Mesa, Arizona, and one vehicle was procured from an employee of the test facility.

Real-time evaporative emissions test data were obtained for thirty-six 1977 to 1989 model year vehicles under conditions representative of a California mid-morning commute. The test procedure involved a cold soak followed by a driving event using the LA92 cycle, followed by a hot soak at 75°F and then a diurnal event where the ambient temperature was increased from 75 to 84°F over six hours. Ambient temperature then decreased from 84°F to 60°F over the next 13 hours and then was increased from 60°F to 75°F over the final five hours of the test.