Measurement of NO in Lieu of NOx in Modal Automobile Exhaust Analysis

Measurement of nitric oxide (NO) has been shown to be an equivalent indication of total oxides of nitrogen (NOx) for the purpose of performing I/M 240 (modal) emissions testing on gasoline powered automobiles. The study uses simultaneous measurements of NO and NO_x taken during I/M 240 transient tests from a large random sample of in-use vehicles. Conclusions are also supported using published chemical reaction models and reaction rate experiments.