This International Standard is intended to provide a common reference to uncertainty estimation in air quality measurement, including measurements of ambient air, stack emission, indoor air and workplace atmospheres. It provides comprehensive guidance and specificstatistical procedures for uncertainty estimation in air quality measurement, implementing the general recommendations of the Guide to the Expression of Uncertainty in Measurement (GUM) to boundary conditions met in air quality measurement. Conditions considered includemeasurands varying rapidly in time, hidden deviations caused by random changes of measuring conditions not corrected for, and the e