Overview
EN ISO 14956:2002 - "Air quality - Evaluation of the suitability of a measurement procedure by comparison with a required measurement uncertainty" - is a CEN-adopted International Standard that defines how to assess whether an air quality measurement method meets a specified measurement quality. The standard applies to procedures whose output is a defined time average and sets out how to estimate measurement uncertainty from method performance, evaluate applicability based on laboratory and field data, and establish requirements for instrument dynamic behaviour.
Key topics and technical requirements
- Estimation of measurement uncertainty
- Derives combined and expanded uncertainty from actual or claimed values of relevant performance characteristics under stationary conditions.
- Uses partial standard uncertainties (e.g., due to calibration, instability, repeatability, reproducibility) to build the combined standard uncertainty.
- Performance characteristics
- Addresses identification and quantification of important sources of uncertainty and assigns them to performance characteristics (sensitivity, drift, interferents, calibration fit, repeatability/reproducibility).
- Introduces weighting/sensitivity coefficients and analytical/model functions to propagate influence quantities to the measurand.
- Dynamic behaviour requirements
- Specifies required performance related to dynamic conditions (response time and behaviour when measurand or influence quantities are time-dependent).
- Assessment of applicability
- Describes evaluation of a method based on laboratory performance and confirmatory field verification programmes.
- Reporting and examples
- Requires documentation of results and includes informative annexes (e.g., default interferent ranges, coverage factor calculations, and example assessments such as UV fluorescence SO2).
Practical applications
- Use EN ISO 14956:2002 to:
- Determine whether an air quality monitoring method meets legislative or project-specific required measurement uncertainty.
- Evaluate and compare instrument or method performance before deployment in ambient monitoring networks.
- Design field verification and quality-assurance programmes that confirm laboratory performance under real-world conditions.
- Define dynamic performance (response time) criteria for instruments used to produce time-averaged outputs.
Who should use this standard
- Environmental laboratories and testing facilities
- Air quality instrument manufacturers and designers
- Regulatory agencies and environmental authorities
- Accreditation bodies and conformity assessment organizations
- Environmental consultants and monitoring network operators
Related standards
- ISO 6879 (referenced normative document) - performance characteristics for air quality measuring methods
- GUM (Guide to the Expression of Uncertainty in Measurement) and VIM (International Vocabulary of Metrology) are referenced for uncertainty concepts and definitions.
For implementation, consult the full EN ISO 14956:2002 text and related normative references to ensure correct application of uncertainty calculations and field verification procedures.