Assessing uncertainty in CEMs data under EN14181

This 23-minute technical session delves into the methodology and implications of quantifying uncertainty in Continuous Emissions Monitoring Systems (CEMS) under the EN 14181 standard. 

Designed for emissions professionals, environmental compliance officers, and instrumentation engineers, the presentation combines regulatory theory with practical implementation. Topics covered include:

• Understanding EN 14181 Uncertainty Framework

  • Definition and legal basis for uncertainty assessment under European standard EN 14181.

  • Required confidence levels and performance targets applicable to CEMS reporting.

• Sources of Measurement Uncertainty

  • Analysis of component sources: sensor accuracy, calibration gas variability, environmental factors, drift, and sampling system influences.

  • Methods to identify and quantify these uncertainty contributors during different testing phases.

• Quantitative Methods for Uncertainty Estimation

  • Use of statistical approaches (e.g., GUM methods) to compute combined uncertainty.

  • Step-by-step example: constructing an uncertainty budget, calculating combined standard uncertainty, and deriving expanded uncertainty for reported emissions.

• QAL2 and Surveillance Test Considerations

  • Integrating uncertainty calculations into Quality Assurance Level 2 (QAL2) validation reports.

  • Application of uncertainty margins in surveillance testing and compliance verification.

• Impact on Compliance and Reporting

  • How uncertainty values influence emissions measurement decision-making.

  • Interpretation of results when uncertainty approaches or exceeds performance thresholds.

• Best Practices and Tools

  • Guidance on using software tools, audit checklists, calibration protocols, and data records to ensure rigorous uncertainty estimation.

  • Recommended practices for continuous uncertainty tracking and documentation.

• Case Study – Real-World Application

  • Application of uncertainty assessment in an industrial deployment under EN 14181.

  • Discussion of challenges encountered, corrective actions taken, and lessons learned for future implementations.

This session equips monitoring professionals with the expertise to execute robust uncertainty calculations, integrate them into EN 14181 QA workflows, and confidently interpret measurement accuracy. It offers a practical, regulatory-aligned roadmap to ensuring CEMS data reliability and compliance.