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The United States Environmental Protection Agency (EPA) has finalized a reporting rule for the Greenhouse Gases (GHGs) emissions including Nitrous Oxide (N₂O) from all sectors of the economy. In addition, EPA and the National Highway Traffic Safety Administration (NHTSA) have been working together on developing a National Program of harmonized regulations to reduce GHGs emissions and improve fuel economy of light-duty vehicles (LDV). As a consequence, the limiting value for N₂O emission from LDV is set to 0.01 g/mile. Considering this regulatory limit of N₂O emission from LDV, if the exhaust gas is diluted and stored in a sample storage bag, the concentration of N₂O becomes very low which requires a highly sensitive analyzer for accurate measurement. In the previous study, an instrument based on Quantum Cascade Mid-IR Laser (QCL-Mid IR) Spectroscopy has been developed for measuring ultra-low level of N₂O in automobile exhaust gas sampled in a sample storage bag.

An analyzer based on Quantum Cascade Laser (QCL) has been developed for chemical sensing of gaseous nitrogen compounds (NO, NO2, N2O and NH3). The QCL can emit lights in a mid-infrared (Mid-IR) region where these nitrogen compounds have strong absorption. This laser optics configuration can give a super fine resolution of the mid-infrared spectrum. Therefore, utilizing this spectrometer can reduce the interference caused by the spectral overlap of co-existing gases in engine exhaust. The developed analyzer has been evaluated using actual engine exhaust to confirm the influence from coexisting gases and the measurement accuracies and stabilities. Very low detection limit (less than 1 ppm) and quick response time (less than 2 sec) have been achieved even with the newly developed analyzer.