Correction of Olfactometry Results for Temperature in Dispersion Modelling
Computer based dispersion modelling to predict the impact of odour releases on neighbours of facilities is often used, and often mandated, for the evaluation of proposed new or modified industrial facilities. Often, the proposed odour emissions are from stacks, the plumes from which can be well above ambient temperatures.
Odour strengths for modelling purposes are measured in odour units (ou). Odour units are dilution ratio, analagous to parts per million by volume (ppmV). Odour units are an expression of the perception threshold of odour sensory panellists. These thresholds occur at specific chemical concentrations measured at laboratory conditions. The difference in temperature between stack and odour laboratory, if not accounted for, can lead to the use of inflated odour emission values when modelling odour emissions from hot stacks.
This paper will demonstrate how the inflated odour emission values can arise, the consequences for dispersion modelling, and propose methods to correct for this inflation factor.