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.