Conversion of the chemical concentration into odour concentration: evaluation of the key parameters

Continuous odour measurements are seldom realised, mainly because of their high costs. They are therefore often substituted by chemical concentration measurements of odorous substances. Then a conversion of the chemical concentrations C (mg m-3) into odour concentrations OC (ouE m-3) is necessary. Several methods are in use for the conversion: the chemical concentration C, the sum of odour activity value SOAV, the sum of odour intensity SOI, the equivalent odour concentration EOC, and the sum of odour activity factor SOAF. These conversion methods are evaluated by comparison with the olfactometric measurements of odorous mixtures. The results indicate that the SOI and EOC methods deliver reliable values for odorous mixtures composed of seven substances, and the accuracy is much better than for the first two methods, since SOI and EOC methods use not only the odour threshold concentration but also the slope of the Weber-Fechner law to include the sensitivity of the odour perception of the individual substances. On the other hand, the SOAF method shows a good precision on the prediction of odour concentrations of real odorous air samples in a waste disposal plant. The reason lies in the fact that the SOAF method includes the interaction effects in the complex odorous air samples