NOx emission survey of selected motor vehicles.

A survey of the NOx emissions of motor vehicles in Metro Manila was conducted. The NOA 7000 Nox-02 Analyzer was required through the DOST-ESEP program. The instrument was positioned at gasoline stations, bus terminals and other locations where vehicles namely buses, mega taxis, jeepneys, tricycles and automobiles were tested for NOx emissions. A total of one hundred four (104) vehicles were tested. The vehicle was kept at idle speed while it was being tested. A metal probe which was connected to the instrument was inserted into the vehicle\u27s tailpipe for measurement of the NOx emissions. The exhaust gas was fed directly into the NOx-02 analyzer, which then reported the measurement in parts per million. Each test ran for four minutes. The data gathered was analyzed for the effct of type of fuel, temperature at the tailpipe, distance travaled, and age of the vehicle on its NOx emission. Very little difference was found between the NOx emissions of leaded and unleaded gasoline-run vehicles. Slightly lower NOx emissions were observed from diesel-run vehicles. NOx emissions increased with increase in temperature. The extent of use of the vehicle had a little effect on its NOx emission. The results of this study may be used as a reference for the setting up of NOx emission standards and the development of technologies for NOx pollution control