Validation measurements to determine the measurement uncertainty in odour emission measurements according to DIN EN 13725:2022

As already reported here on 8th February 2023, the VDI working group "Determination of odour concentration with dynamic olfactometry", which is part of the VDI/DIN Commission on Air Quality Control (KRdL), has initiated the project "Validation measurements to determine the measurement uncertainty in odour emission measurements". Boris Zimmermann and Frank Müller from our branch office in Gelsenkirchen are part of the working group as representatives of Müller-BBM Industry Solutions GmbH.

The aim of the project was to validate the new method for determining the measurement uncertainty specified in DIN EN 13725:2022 on the basis of comparative measurements on real environmental samples. The State Office for Nature, Environment and Consumer Protection of North Rhine-Westphalia (LANUV) and the VDI were involved in the project as supervising authorities.

Within the scope of this project, odour measurements were carried out at the sewage sludge drying facility of the Bottrop sewage treatment plant (Emschergenossenschaft/Lippeverband) on 11th January 2023. In addition to the colleagues from our Gelsenkirchen branch, eleven other accredited measuring facilities notified in accordance with Section 29b of the Federal Immission Control Act (BImSchG) took part in these validation measurements, in which a total of 240 odour samples were taken.

Subsequently, all odour samples obtained were subjected to an intensive test with regard to a standard-compliant measurement procedure as stated in DIN EN 13725:2022 and then - taking into account all odour samples obtained in accordance with the relevant standards - the extended measurement uncertainties were determined according to DIN EN ISO 20988:2007 (methods A6 and A7), DIN EN 13725:2022 and VDI 3884 Part 1:2015, among others.

The results of the project were presented at the 10th VDI symposium "Odours in the Environment 2023" in Leipzig.

It can be concluded from the results that the standard method used to report the measurement uncertainties of olfactometric measurements in accordance with VDI 3884 Sheet 1:2015 until the new version of DIN EN 13725 was issued in 2022 shows measurement uncertainties that are too low. However, the method currently used to determine the internal laboratory measurement uncertainty in accordance with DIN EN 13725:2022 is also to be classified as technically questionable. This is in particular due to the differences between negative and positive measurement uncertainty and an unrecognisable correlation between the measurement results for n-butanol and environmental samples. Here, the A6 method according to DIN EN ISO 20988 seems to be a suitable and proven alternative. A corresponding proposal to introduce this method for the calculation of the measurement uncertainty of olfactometric measurements was submitted to the relevant national bodies.

The validation measurements were supported by the VDI/DIN Commission on Air Quality Control (KRdL), FKZ: 372201I001.

Odours - Müller-BBM Industry Solutions GmbH (


The validation measurements were carried out in accordance with DIN EN 13725.

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