National Physical Laboratory

METNH3: Metrology for Ammonia in Ambient Air


The measurement of ammonia in air is a sensitive and priority issue due to its harmful effects on human health and ecosystems. The European Directive 2001/81/EC on national emission ceilings for certain atmospheric pollutants (NEC) regulates ammonia emissions in the Member States. However, there is a lack of regulation regarding the analytical techniques to use, the maximum allowed uncertainty, the quality assurance and quality control (QC/QA) procedures and the metrological traceability infrastructure to underpin ammonia measurements. Discrepancies among European NMIs for primary ammonia reference gas standards and measurement techniques far above ambient air levels (30 to 50 μmol/mol) jeopardise not only the credibility of instrumental performance, due to poor calibration, but also the scientific value of extensive ambient air monitoring by national networks and the international exchange of scientific data.

Beyond the state of the art

This project will develop the metrological traceability for the measurement of ammonia in air. It will focus on:

  • Developing high accuracy ammonia standards by static and dynamic gravimetric generation methods
  • Elucidating the former discrepancies between standards and methods among NMIs (CCQM-K46)
  • Developing and characterising laser based optical spectrometric standards
  • The applicability of open-path and extractive measurement techniques as optical transfer standards
  • Establishing transfer from high-accuracy standards to field applicable methods by applying characterised exposure chambers and field sites for validation and comparison experiments
  • Evaluating the performance of different instruments and measurement methods at ambient molar fractions (0.5 to 500 nmol/mol) under both real air and artificial conditions with proficiency tests


  • The results of this joint research project will enable NMIs to offer traceable and concordant calibration and measurement capabilities at the required amount fractions (20 to 500 nmol/mol ammonia in air) to disseminate SI traceability
  • Basis for comparing measurement results across networks among various techniques and will allow standardising analytical techniques
  • Identifying changes due to implementations of environment abatement policies, minimising the uncertainties in current emissions inventories, and providing independent verifications of atmospheric model predictions.
  • Provision of validated measurement tools to enable EU SMEs developing new monitoring technologies to deliver improved instrumentation to the market
  • Defensible compliance with legislation (2001/81/EC) and improvements in quality of life

Contact us

For further information on this research, please contact us:

METNH3 project website
Customer enquiry tel: +44 20 8943 8715

Last Updated: 23 Dec 2014
Created: 10 Dec 2014


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