A potential remote sensor of CO in vehicle exhausts using 2.3 mu m 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-mod ulation-spectroscopy (WMS) technique, 20 ppm sensitivity with a detection b andwidth of similar or equal to1.5 kHz is demonstrated in laboratory experi ments, which implies the ability to monitor CO emissions from even the clea nest combustion-powered vehicles. The influence of the temperature and comp osition of the exhaust gas on the inferred CO concentration through both li nestrength and linewidth is also investigated and we propose a novel approa ch to reduce these effects to +/-3% in the typical exhaust temperature rang e of 300-700 (K) under bar. Thus, sensitive and remote measurements of vehi cular CO effluent are possible without knowing the exact temperature or com position of the exhaust. This influence of temperature is further exploited to suggest a two-line CO2-absorption thermometry method with a large tempe rature sensitivity to identify cold-start vehicles.