Diesel Emissions as Predictors of Observed Diesel Odor

The use of diesel exhaust-emissions measurements to predict the observed odor from diesel engine exhaust has been studied, using a group of 31 trucks and buses powered by a variety of diesel engines. Regression analysis of gaseous emissions at a variety of conditions has resulted in equations for use in predicting odor. Acrolein, carbon dioxide, total hydrocarbons, selected light hydrocarbons, nitric oxide, carbon monoxide, and aliphatic aldehydes have been related to perceived odor. Some of these exhaust products are odorous and some are nonodorous yet indicative of the completeness of combustion. The empirical method, however, is somewhat less reliable than the observed odor based on a trained panel rating supra-threshold levels in terms of the PHS Quality-Intensity Odor Rating kit. In general, the greater variety of measurements and the fewer type of engines will increase odor prediction accuracy.