System and Utility Considerations for Analyzer Calibration and Measurement of Low Concentrations in Automotive Exhaust

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. Additional gas transfer considerations will be investigated. Typical gas impurities will be introduced to investigate system cleanliness recovery requirements.