Measurement uncertainty in odor emission measurements - conclusions from 10 years of proficiency testing

Dynamic olfactometry according to EN 13725 is widely used as the standard method for quantifying odor emissions, yet its measurement uncertainty remains debated. This study evaluates ten years (2015–2024) of proficiency testing data, including more than 1900 measurements on a stack simulator and compares these with over 1000 real-world emission analyses. The key findings are a repeatability standard deviation ( s r ) of 0.53 dB od and a reproducibility standard deviation ( s R ) of 2.55 dB od for general odors. The expanded uncertainty (95% confidence) is estimated at 5.10 dB od . For the reference odorant n -butanol, s R was lower (1.87 dB od ), reflecting assessor pre-screening. Importantly, the sample composition (single substances versus complex mixtures) did not impact variability. Our results demonstrate that proficiency tests on a stack simulator accurately reflect real-world variability, challenging previous assumptions of lower uncertainties (≤ 2 dB od ). The findings underscore the need for revised uncertainty estimates in regulatory frameworks. This work provides the most comprehensive empirical basis to date for optimizing the implementation of EN 13725 and guiding future standardization efforts. • Analysis of more than 1900 odor emission measurements from proficiency tests on a stack simulator and more than 1000 from measurements on actual emission sites • Repeatability standard deviation s r and reproducibility standard deviation s R are determined • Typical measurement uncertainty for odor emission measurements is estimated to be much higher than previously thought • Sample composition (from single odorant substances to complex mixtures) has no effect on the performance of the olfactometry