The chemical composition of air samples requires a sophisticated instrumentation, able to guarantee high sensitivity in order to detect the presence of traces of osmogene substances with a very low sensory threshold (odour threshold, OT).
The air sample taken in instantaneous mode and stored in Nalophan or Tedlar bags is transferred to an absorbent vial and analysed by gas chromatography-mass spectrometry (GC-MS) equipped with thermal desorption unit, according to EPA TO-15 and TO-17 methods, as recommended in Annex 4 of the Lombardy Region Guidelines (“Guidelines for the characterization and authorization of gaseous emissions into the atmosphere from odour-impact activities” issued with the Regional Government Resolution of 15 February 2012 – No. IX / 3018).
Routinely, in each sample, more than one hundred and fifty analytes of odorous interest are examined, belonging to the most diverse chemical classes with a wide spectrum of sensory thresholds.
This technique is also used to identify the characteristic chemical traces of emissions, which are then sought at the sensitive receptors (in samples of ambient air) in order to identify the sources responsible for the odour impact on the surrounding area.
When the toxicological aspect of odour emissions is a primary need, canister-based sampling is used for the set period of time, even over several days, at the sensitive receptors in order to evaluate the level of exposure of the human population to the emitted substances.