National Physical Laboratory

The State of Stack Emission Monitoring in the UK

Analysing proficiency testing data for SO2, NO and particulates

Image courtesy of iStockphoto
Image courtesy of iStockphoto

The performance of analytical laboratories participating in proficiency testing schemes has been well reported in the literature. However, there is a relative dearth of analysis of the performance of the stack testing industry, tasked with monitoring emissions to air from refineries, cement works, fibreglass manufacturers, power stations, combustion plants, etc.

Data were analysed from three proficiency testing schemes run by the National Physical Laboratory, UK; Calibration Gas Scheme (gas bottle certified reference materials), Gas Measurement Scheme (testing the entire measurement system using a Stack Simulator Facility) and Particulate Scheme (foil shims and salt solutions). It was found that since inception of the schemes (circa 2000) the bulk of the industry had maintained performance (see SO2 data below) whilst individual companies showing 'unsatisfactor' proficiency successfully took corrective action as demonstrated in subsequent rounds.Hence, the schemes were having the desired effect in terms of adding validity to the quality of UK emissions data and ensuring standards were ultimately maintained in accordance with the requirements of the EU's Industrial Emissions Directive.

State of Stack Emission Monitoring in the UK - stack testing boxplot

Boxplot showing UK stack testing industry proficiency distribution across 7 rounds of testing from 2000 to 2011 for measurement of SO2 emissions. Where z-score is the number of deviations beyond a permitted tolerance derived from the uncertainty requirements in the Industrial Emission Directive and a z-score of |z| ≤ 2 is considered 'acceptable' proficiency.


Our full analysis was published in Accreditation and Quality Assurance, Volume 18, Issue 6:
State of UK emissions monitoring of stacks and flues: an evaluation of proficiency testing data for SO2, NO and particulates
Marc D. Coleman, Rod A. Robinson, Matthew B. Williams, Martin J. Clack, David M. Butterfield.

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Last Updated: 24 Feb 2014
Created: 4 Feb 2014

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