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Ammonia sampler study

The need

Unlike other regulated pollutants, the concentration of ammonia in the UK is still increasing. Ammonia damages sensitive environmental habitats and is responsible for formation of PM2.5 which harms health.  To gain insight into the impact of ammonia, it is therefore essential that devices that monitor levels in air are assessed for accuracy. 

The impact

We have utilised our Controlled Atmosphere Test Facility (CATFAC) to assess the accuracy of existing ammonia monitoring technologies. These tests identified for the first time that there was considerable variability in the accuracy of ammonia measurements between different commercial designs of diffusive and pumped sampling devices routinely employed in the field.


Figure 1: Photograph of NPL’s Controlled Atmosphere Test Facility (left) and intercomparison summary (right) of the mean of the reported ammonia concentrations for diffusive and pumped samplers expressed as a percentage deviation from the reference values.

Through the application of metrology, we have helped UK and EU industry with new traceable values of ammonia diffusive sampling rates and a determination of uncertainty budgets, which delivered improved accuracy and agreement between different types of samplers monitoring NH3 in the field.

NPL has convenorship of CEN TC264 WG11 on diffusive samplers, and the results of this study was critical in the development of BS EN 17346:2020 - Ambient air standard method for the determination of the concentration of ammonia using diffusive samplers, which was published in 2020 [2]. It has also informed independent decision-making in national networks in support of the Defra’s National Air Quality Strategy, EU Directives and UNECE.

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