Type approval of instruments and uncertainty calculations in the new EN-standards for the measurement of SO2, NO2,CO and O3 in ambient air

The new European directives for ambient air quality ore setting data quality objectives for the measurement of air polluting compounds. On request of the European Commission a working group of CEN 264 "Air quality" has developed standards with which these data quality objectives could be realised. Next to the measurement method itself, sampling procedure and quality assurance and quality control, these standards are dealing with type approval tests of instruments and uncertainty calculations of measurement data. Explanation is given about some of the considerations for the choices made by the working group in developing the requirements for performance characteristics, in developing the test methods to establish the values of these performance characteristics and in developing the uncertainty calculations.