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Vehicle interior air quality (VIAQ) measurements are currently conducted using the offline techniques GC/MS and HPLC. To improve throughput, speed of analysis, and enable online measurement, specialized instruments are being developed. These instruments promise to reduce testing cost and provide shortened analysis times at comparable accuracy to the current state of the art offline instruments and methods. This work compares GCMS/HPLC to the Voice200ultra, a specialized real-time instrument utilizing the technique selected ion flow tube mass spectrometry (SIFT-MS). The Voice200ultra is a real-time mass spectrometer that measures volatile organic compounds (VOCs) in air down to the parts-per-trillion level by volume (pptv). It provides instantaneous, quantifiable results with high selectivity and sensitivity using soft chemical ionization.

Two different implementations of Partial Flow Dilution (PFD) methodology designed for gravimetric particulate matter (PM) sampling are evaluated for applicability to light-duty chassis emissions testing. Filter PM measurements were collected and compared to constant volume sampler (CVS) full dilution tunnel PM filter measurements and other real-time PM measurement technologies, using gasoline vehicles generating a range of 0.1 to 10.0 mg/mile PM. Exhaust samples were collected for each phase of the Federal Test Procedure (FTP-75) with a fourth filter sample collected for the US06 supplemental cycle. Both PFDs satisfactorily met proportionality criteria for conventional combustion engines, but some improvements are needed for hybrid electric vehicles (HEVs). The PM mass collected scaled linearly with the CVS tunnel samples, with slopes of 1.03 and 0.74 for the two PFDs.

Several vehicle-level test procedures exist for measuring and analyzing volatile organic compound (VOC) emissions from new vehicle interiors. In this paper, four vehicle-level procedures were examined to determine the effect of interior air temperature (driver's side breath position), ventilation, vehicle age, and solar load (intensity and source) on the total VOC concentration. A new vehicle (11 days old) was tested over five weeks at interior air temperatures of ambient, 40°C, and 50°C with the ventilation on and off. Three sources of solar load were examined with loads between 600 and 1,100 W/m₂. The three sources of solar load were 5-Zones of halogen lights, an SC03 test site with metal halide lights, and the sun. Total VOCs were measured (μg/m₃) as well as individual hydrocarbons including formaldehyde. Six temperature points in and around the vehicle were monitored over the course of each test.

In Fall of 2001, a new emissions test cell was installed at Ford Motor Company that was specifically designed for precise low-level measurements (as described in Reference 6). The primary design focus for this cell was to ensure that optimal measurement capability was available to test vehicles that meet the stringent Partial Zero Emission Vehicle (PZEV) tailpipe requirements (NMOG = 10 mg/mile, NOx = 20 mg/mile). Over the past four years, there have been numerous improvements to the operational and Quality Assurance (QA) practices used in the PZEV Test Cell. Several investigations have also been performed to demonstrate the quality of its emissions measurements. Finally, a number of “lessons learned” have been documented from our experiences with PZEV measurements and with testing hybrid-electric vehicles. This paper summarizes these findings as a reference for others interested in low-level emissions measurements.

The on-going regulatory emphasis on reducing vehicle emission levels and increasing fuel economy has resulting in numerous efforts to improve the technology used to obtain these measurements. For example, raw exhaust flow meters are being implemented to provide improved tailpipe (i.e. modal) emission measurements as part of the vehicle development process. In addition, new sampling system technologies (e.g. partial flow dilution systems) are being implemented that use either synthetic air or catalyzed/dried ambient air to dilute exhaust samples. With these new technologies, however, often comes an increased sensitivity to leakage from both the test equipment and from the hoses/connectors used to route the vehicle's exhaust gas to the test equipment. In the case of the exhaust flow meter, a leak upstream of the measurement zone will provide an inaccurate flow reading. With an emissions sampling system, an exhaust leak will result in inaccurate emissions and fuel economy readings.

Exhaust flow measurements are becoming increasingly important to ensure accurate emissions measurement on both a continuous and averaged (i.e. bag) basis. When performing continuous mass measurements of hydrocarbons, nitrous oxide, carbon monoxide, carbon dioxide and other pollutant/greenhouse gases, the exhaust flow measurement is critical to the task of providing an accurate result. In addition, the acceptance of the Bag Mini-Diluter (BMD) for low-level emissions measurements has amplified the need for an accurate exhaust flow measurement. With the BMD, there is a direct correlation between fuel economy/emissions accuracy and exhaust flow measurement accuracy. To meet these demands, several new exhaust meters have emerged in the last few years that encompass promising technology and unique solutions to the traditional problems that tend to complicate exhaust flow measurements.

With the recent acceptance of the Bag Mini-Diluter (BMD) for low-level exhaust emissions measurement, there is an increased interest in exhaust flow measurement technology throughout the industry. Accurate tailpipe exhaust flow measurements can be considered the most “difficult” aspect of Bag Mini-Diluter systems due to the heat, water content, and transient behavior of the samples. Acceptance by the EPA and ARB of the Bag Mini-Diluter sampling system was based on the design and performance of the Flow Technologies E-Flow system with UGF-5 ultrasonic electronics. A number of noteworthy advancements have been made to this exhaust meter since the Agency's acceptance, and there appears to be a number of new technologies entering the market. At this time, ultrasonic flow measurement is the most prevalent and robust technology, however, other alternatives are worthy of consideration.