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 mot or vehicles. The system uses a monostatic source-detector platform and a retroreflector. It has been shown to be able to measure the emissio ns from individual vehicles at highway speeds. Excellent detection sen sitivity 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 syste m is also capable of measuring CO, NH3, H2CO, CH3OH, and other small m olecules in vehicle exhaust.