Both olfactometry and physical-chemical analysis are two methods used to evaluate the somehow relative annoyance caused by odorous substances. These techniques have several advantages and also some drawbacks although they can provide complementary information.

  With the olfactometry technique odour threshold can be quantified but in most cases these parameters cannot be chemically linked to a substance or group of substances. On the other hand, a physical-chemical analysis can identify single substances that could be related with odorous episodes, but in most of the cases these relation is not possible. Physical-chemical analysis proportionates also information about the toxicity of certain odorous gases, however, there will hardly be a link between concentration of a substance and odour annoyance using this technique. As a short example, more than 500 molecules have been identified in a sample taken from a landfill (terpenes, sulphides, aldehydes, acids, acetones, alcohols, aromatic compounds, chlorides, esters, etc.).

  When measuring odours, 2 different methods can be used depending on the characteristics of the Odours (1).

  •   Physicochemical Methods: Gas Chromatography, FID, piezoelectric sensors (electronic noses), colorimetric tubes, etc.
  •   Sensory methods: Olfactometry, Nasal Ranger, psychometric assessment, etc.

  The physical-chemical methods are suitable when the Odorous compound is known or when we pretend to monitor the emissions of certain installations in continuum to control the presence of gas leakages associated with odorous compounds. This methods are not very specific or sensitive nowadays.

  Although it is a relatively new technique, Olfactometry is presented as the future standard to measure odours until other devices, such as the electronic nose, are further developed.

 Bags with odorous gases are quickly brought to the laboratory and Odour Concentration is evaluated by means of a Dynamic Olfactometer, which is basically a dynamic dilution system.

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