Field Intercomparison of Air Quality Measurements in Switzerland

Abstract

As part of a national quality assurance programme of the Cercl'Air in cooperation with the Swiss Federal Office for the Environment (FOEN) and the Swiss Federal Office of Metrology (METAS) there have been intercomparisons of air quality monitoring stations of interested institutions in regular intervals since 1988. The former approach, alternating between calibrations with test gases of measuring stations on site and gathering mobile measuring units for additional comparative measurements every second year, had to be modified as mobile measuring stations have become increasingly sparse over the last years. The idea was to find a solution to combine the two types of intercomparison in one campaign. The problem was solved by assembling a mobile reference station for measuring air pollution, with the addition of equipment to provide test gases for the candidate instruments. With this mobile measuring unit, calibration with test gases and comparative measurements could be performed on site at the candidate air pollution monitoring stations. The results of the 2007 intercomparison campaign showed that the achieved quality improvements in air pollution measurements over the last twenty years – decrease of expanded uncertainties in intercomparisons by a factor of 4 to 7 depending on the type of pollutant – could be sustained.