Room-temperature mid-IR lasers for on-line measurements of trace combustion generated pollutants

Measurements of NO and CO in combustion exhaust gases are reported using thermo-electrically cooled, mid-IR quantum cascade lasers operating near 5.26 and 4.62 μm respectively. Measurements of NO are performed in an insulated exhaust duct of a C₂H₄-airflame at temperatures of approximately 600 K. CO measurements are performed above a rich H₂-air flame seeded with CO₂ and diluted with N₂ to 1150 K. Sensitivities on the order of 0.36 ppm-m are achieved in the case of NO and 0.21 ppm-m in the case of CO using a balanced ratiometric detection technique. Comparisons between measured and predicted water-vapor and CO₂ interference is discussed.