A tunable diode laser system for the remote sensing of on-road vehicle emissions

A tunable infrared laser differential absorption spectrometer (TILDAS) has been developed to measure air-pollutant emission from on-road motor vehicles. The system uses a monostatic source-detector platform and a retroreflector. It has been shown to be able to measure the emissions from individual vehicles at highway speeds. Excellent detection sensitivity is obtained with measurement precision as small as 3 ppmv of the exhaust under ideal conditions. Long path lengths (100 m or more) can be achieved due to the coherent nature of laser radiation. NO, N2O, and NO2 emissions have been measured with this instrument. The system is also capable of measuring CO, NH3, H2CO, CH3OH, and other small molecules in vehicle exhaust.