I'm confused with the measurement of odor intensity introduced in VDI 3882 Part-1. Should dilution series be presented? Could the panellist just smell the undiluted sample and classify the odor impression with number 0~6? And what does "the series of measurements shall be repeated (at least twice; 3 runs)" mean?
Odor concentration and intensity level should be measured by selected average noses (panelists with butanol odor threshold value between 20~80ppb) and stable performance (standard deviation). For a stable performance panelist, he/she may choose a different intensity level in random sniffing tests. The more measurement repeats, the average value may be more accurate for a normal distribution data. However both odor concentration and intensity measurements are time consuming and costly. This is why a minimum repeats are required.
Hope it answered your question.
Xinguang Wang Thanks for your answer. As far as I know, odor concentration can be measured according to EN 13725, and a dilution series should be prepared and tested. If I have one sample to test its odor intensity, should I prepare a dilution series? Or the panellist smell the sample directly, and report the intensity level? By the way, are there any other standards about odor intensity measurement in Europe? Many thanks.
Odor intensity measurement should follow the standard method as you quoted before. Like odor concentration measurement, odor intensity measurement also requires sufficient number of panelists and a dynamic olfactometer. For a single panelist, his/her sensory response may be different when presented with the same sample. So the minimum repeats are also required. The link below summarized the measurement that may be useful to you:
https://www.der.wa.gov.au/images/documents/your-environment/air/publications/odour-methodology-guidelines.pdf
In my understanding, it might be hard to specify the intensity level by sniffing the sample directly without comparing. Presenting panelists with a series of dynamic dilution steps may help them select a reasonable scale value for each dilution step. It is also possible to relate intensity values with odor concentrations for each panelist. The relationship curve can also be used to check if a panelist's intensity value selection is reasonable for a single dilution step in a series of dilution steps.
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