Odor analysis

An odor-active substance from the spectrum of volatile organic compounds (VOC) is characterized by an odor threshold, i.e. the concentration-dependent perception of an odor by the olfactory receptors in the human nose and the ability to describe (verbalize) its quality.
Unpleasant odors are assigned to the spectrum of harmful substances because they are often the cause of complaints. However, the nature of an odor does not cause damage. An off-odor is defined as:

• an extremely unpleasant smell (e.g. fecal, burnt) or
• an unexpected or pleasant odor emitted by a source (place/material) that smells differently than expected (e.g., fruity wall paint, carpet smelling of solvent).

An objective evaluation is made all the more difficult by the fact that different people perceive odors in different ways. On the one hand, olfactory perception follows a normal Gaussian distribution curve, which is the same for all human senses (auditory, visual, haptic). On the other hand, it is extremely difficult to detect odorous substances using conventional analysis methods to determine the chemistry of indoor air, since many odor-active compounds have such low odor thresholds that they are far below the detection limits of chemical-analytical measurement systems. Therefore, a specific analysis method is needed to detect them:

Olfactory analysis

To identify and quantify odorous substances, standard instrumental analysis (gas chromatography-mass spectrometry, GC-MS) is combined with human perception (olfactometry, GC-MS/Olf, “GC sniffing”): The researchers “sniff at the analysis device”. This allows off-odors to be identified, as well as the source of the odorous substances and processes responsible for their formation to be determined. Specially-trained odor experts (sensory assessors, flavor chemists) are involved in the analysis procedure. These people are able to describe odors quickly in a time-resolved manner and to assign them to the signals measured.

Sensory panel

The olfactory characteristics of technical materials or the interiors of means of transport (e.g. cars or airplanes) are assessed by a group of test persons in accordance with national and international standards and industrial guidelines. A trained or untrained panel assesses the intensity (see odor dosing systems), hedonics and acceptance of  the odors. We regularly train a panel of approx. 30 test persons, who can classify intensities on the basis of defined scales and describe odors with a recognized vocabulary.

Methods

Gas chromatography-olfactometry (GC-sniffing), sensory testing, determination of odor thresholds (e.g. according to Cometto-Muniz, Cain 1998, DIN EN 13725), trained and untrained panel, DIN ISO 16000-28, DIN ISO 16000-30, ISO 12219-7, VDI 3882 VDI 4302, VDA 270.

Fraunhofer IBP is accredited by the DAkkS as an odor analysis center using a trained panel.