On odour tolerability criteria from odorant instrumental monitoring

At present one of the most accepted criteria for assessing tolerability for environmental odour impacts is based on a modelling approach that requires the characterizations of the odour flow rates from stationary sources, definition of both a digital terrain model of the studied area and of relevant meteorology during the considered period of time, so to provide an estimate of the areas where the number of hours exceeds specified hourly odour threshold (e.g. 1, 3 or 5 OUE). Often the 98th percentile of hourly peak odour concentration is considered at sensible receptors. In the case of complex odour sources or if the emitting entity is not collaborative, the experimental approach focused on receptor instrumental monitoring can provide a tool for the assessment of odour nuisance tolerability, so to foster or to force mitigation actions on odour emission sources. Since nowadays instruments allowing single (e.g. H2S monitoring instruments) or multiple (e.g. e-noses) odorant concentration monitoring are available, and they are often positioned at sensible receptors, experimental measurement of the exceedance of odour threshold can be provided, if consensus odour threshold values for the odorant are available. Also for the experimental approach, the 98th percentile of hourly odour concentration can be provided. A case study based on H2S monitoring is proposed; extension to e-noses application is possible, providing their active and efficient presence in the field 12 months a year. Pros and cons of different approaches and criteria will be discussed.