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Automotive emissions have been regulated to very low mass emissions. Various collection techniques have been utilized to measure the emitted gases. Some sample collection techniques utilize dilution gases that have concentrations below ambient air background values. For these applications analyzers with very low ranges have been produced. When using analyzers with ranges below 10 ppm, gas accuracy and impurities become very critical to the successful operation of these analyzers. A general demonstration of analyzer accuracy will be presented for various ranges. The availability and accuracy of the reference gases will be discussed. The relationship between the accuracy of the gas labeling and the analyzer's calibration accuracy will be evaluated. Gas delivery components can also affect the purity of zero gases and the accuracy of gas mixtures. Oxygen cleaned gas cylinder regulators will be compared to standard regulators for THC background contribution.

In response to the appearance of formal regulations, CFR part 1065 subpart J, a new in-use emission measurement system was developed, the OBS 2000. The OBS 2200 uses partial-vacuum analyzers. The heated flame ionization detector (HFID), heated chemiluminescence detector (HCLD) and heated non-dispersive infrared analyzer (HNDIR) are all upstream of the sample pump. This design decreases the response time of the analyzers, lowers power consumption and minimizes the overall dimensions of the system by avoiding the use of a heated sample pump. The size of the heated zones is also minimized to reduce power usage. Typical power consumption of analyzer unit is less than 500 W. The overall dimension of the main unit is 350mm (W) × 330mm (H) × 500mm (D). Analyzer linearity checks as required by new regulations [1] for all available ranges will be presented along with cut point accuracies relative to full scale and percentage of point.