Influence of odour concentration and individual odour thresholds on the hedonic tone of odour from animal production

Odours constitute a problem when they affect the health of those exposed or when their character and intensity cause annoyance. Odour concentration and the hedonic tone of odours are of interest when setback models are used to predict annoyance in the neighbourhood of odour emitting operations. An experiment was made with the objective of studying the relationship between the odour concentration and the hedonic tone of odours from pig, poultry and dairy operations. A further objective was to identify individual factors of importance for rating of the hedonic tone. A panel of 16 persons was engaged to rate the hedonic tone and for each panel member the individual odour threshold for n-butanol was estimated. Odour samples from poultry and livestock buildings were analysed for odour concentration following European guidelines. The panel members rated the hedonic tone of various odour concentrations. Odour concentration explained much of the hedonic tone of odour from pigs, pig manure and laying hens. For Odour from dairy cows, the odour concentration explained comparatively less. On a hedonic scale, where 0 is neutral and −4 is extremely unpleasant, an odour concentration of 14–16 European odour units (ouE) m−3 from pig and poultry houses was rated to −1. On the same scale, an odour concentration of 37 ouE m−3 from a cow shed was rated to −1. Individual odour thresholds were found to be important for rating of the hedonic tone. The rating of the hedonic tone showed similarity to odour intensities reported in other studies.