Matching Continuous Monitoring and Bag Olfactometric Sampling at the Source: a Case Study

The sampling of odorous emissions is a fundamental step in correctly quantifying odour concentration. Its importance was strongly emphasized in the recent Italian legislation (MASE, 2023), which describes strict constraints for conducting olfactometric sampling. In particular, for point sources, it is necessary to assess the variability of the source to evaluate any spikes in emissivity and then sample consistently with the trend of this emissivity. Therefore, this study aims to conduct a field sampling campaign that meets the criteria mentioned in the Italian recent directive, combining olfactometric sampling with continuous monitoring of the source using portable PID instrumentation. The results obtained during this preliminary monitoring campaign highlight that the variability in VOC emissions is not strictly correlated with potential variability in terms of odour concentration. Indeed, despite the variations observed in continuous measuring at the source, the odour concentration measurements remained stable throughout the monitoring period. Chemical speciation of samples identified high concentrations of propene, varying in accordance with PID reading, while the odour potential was primarily due to lower concentrations of octene and nonene, which remained relatively constant. These results indicate that continuous monitoring emission variability does not necessarily translate into odour concentration variability.