Remote sensing of on-road motor vehicle emissions by DOAS and TDLAS techniques

in the past decade interest has focused on the remote analysis of emissions from motor vehicles using spectrometric techniques, driven by recognition of the fact that a very large proportion of the environmental damage done in this way originates with a small percentage of vehicles. Several instrumentation manufacturers now market such devices, and others are developing new technologies that will offer opportunities for enhanced performance and lower cost. In this paper we demonstrate the prototype design of vehicle emission remote sensing system by differential optical absorption spectroscopy (DOAS) and tunable diode laser absorption spectroscopy (TDLAS). In this design, vehicle emissions will be measured when they past a on road remote sensing station while driving along a road. The concentrations of hydrocarbons (HC) and Oxides of Nitrogen (NOx) are measured by DOAS, and the concentrations of Carbon Monoxide (CO) and Carbon Dioxide (CO2) are measured by TDLAS. The measurement precisions for CO and CO2 are 0.25%, and the detection limits for HC and NO are +/- 250ppm.