A potential remote sensor of CO in vehicle exhausts using 2.3 μm diode lasers

The potential for on-road remote sensing of vehicle exhausts using 2.3 mum diode-laser-absorption-based CO sensors is examined. Using a wavelength-modulation-spectroscopy (WMS) technique, 20 ppm sensitivity with a detection bandwidth of similar or equal to1.5 kHz is demonstrated in laboratory experiments, which implies the ability to monitor CO emissions from even the cleanest combustion-powered vehicles. The influence of the temperature and composition of the exhaust gas on the inferred CO concentration through both linestrength and linewidth is also investigated and we propose a novel approach to reduce these effects to +/-3% in the typical exhaust temperature range of 300-700 (K) under bar. Thus, sensitive and remote measurements of vehicular CO effluent are possible without knowing the exact temperature or composition of the exhaust. This influence of temperature is further exploited to suggest a two-line CO2-absorption thermometry method with a large temperature sensitivity to identify cold-start vehicles.