ISO 20988:2007

Overview - ISO 20988:2007 and measurement uncertainty in air quality

ISO 20988:2007 - "Air quality - Guidelines for estimating measurement uncertainty" provides practical, statistical guidance for uncertainty estimation in air quality measurements. It applies the general recommendations of the Guide to the Expression of Uncertainty in Measurement (GUM) to the specific boundary conditions of air quality monitoring, including rapidly varying measurands and the presence of bias in observation series. The standard covers ambient air, stationary source emissions, indoor air, workplace atmospheres, and meteorology.

Key topics and technical requirements

• Application of GUM principles to air quality: adapts GUM concepts for field and laboratory conditions typical of air monitoring.
• Boundary conditions addressed: rapid temporal variation of measurands and systematic effects (bias) in series of observations.
• Categories of measurement methods considered:
  • Methods corrected for systematic effects using reference materials.
  • Methods calibrated by paired measurements with a reference method.
  • Methods unbiased by design (no correction needed).
  • Methods used with known deliberate bias.
• Experimental designs: supports both a direct approach (single experimental design) and an indirect approach (combination of experimental designs) for providing input data.
• Statistical procedures: Type A (statistical analysis of series) and Type B (other sources) evaluation of uncertainty, variance and covariance estimation, combined standard uncertainty, expanded uncertainty, coverage factor and coverage probability.
• Practical reporting: guidance on specifying objectives, representativeness of data, estimation of variances, degrees of freedom and presentation of uncertainty in measurement reports.
• Informative annexes: testing coverage probability, Type A methods for common experimental designs, and worked examples.

Practical applications

• Use ISO 20988:2007 to quantify measurement uncertainty for monitoring networks, emissions compliance testing, workplace exposure assessments, and meteorological measurements.
• Helps laboratories and field teams demonstrate traceability, support method validation, and produce defensible uncertainty budgets for regulatory reporting and quality assurance.
• Useful when measurements are affected by rapid fluctuations, intermittent bias, or mixed data sources.

Who should use this standard

• Air quality laboratories, environmental monitoring networks, regulatory agencies, method developers, and statisticians involved in uncertainty estimation for ambient air, emissions, indoor air, workplace monitoring and meteorology.

Related standards

• ISO/IEC Guide 98 (GUM) - foundational guide for expressing measurement uncertainty.
• ISO 11222 - addresses uncertainties from incomplete time-coverage (complements ISO 20988 for temporal coverage issues).

Keywords: ISO 20988:2007, measurement uncertainty, air quality, GUM, uncertainty estimation, ambient air, stationary source emissions, indoor air, workplace atmospheres, meteorology.