Proficiency testing scheme, Measurements of inorganic gaseous pollutants (SO2, CO, O3, NO and NO2) in filtered ambient air, 18-21 March 2024 Ispra, Italy : European Commission harmonisation programme for air quality measurements

Within the harmonisation programme of Air Quality monitoring in Europe the European Reference Laboratory of Air Pollution (ERLAP) organises Proficiency Tests (PT). From 18-21 March 2024, eleven Laboratories of AQUILA (Network of European Air Quality Reference Laboratories, including ERLAP) gathered in Ispra, Italy, for a laboratory comparison exercise in Ispra (IT) to assess their proficiency in analysing inorganic gaseous air pollutants (NO, NO2, SO2, CO and O3), covered by the European Air Quality Directive 2008/50 EC [1] and its last amendments 2015/1480/EC [42]. Ecomaks laboratory did not participate to O3 and ACES laboratory to SO and CO2 measurements, respectively. The proficiency evaluation, where each participant's bias was compared to two criteria (z/z'-score and En-score), provides information on the current situation and capabilities to the European Commission and can be used by participants in their quality control system. In agreement with all participants an evaluation of SO2 concentration measured as interference during NOx measurement has been carried out. Evaluation based on z/z'-scores indicated that 89.2% of the reported results were satisfactory. In contrast, consideration of the En-score revealed that 78.8% of all values met satisfactory criteria. Overall, the performance for both indicators was below the average typically achieved in exercises of this type. Considering the reproducibility evaluation, the results among AQUILA participants at the highest generated concentration levels are 9.9% for CO, 12% for NO, 11% for NO2, 4.5% for O3, and 11% for SO2, all of which fall within the objectives derived from criteria set by EN standards. However, NO, NO2 and SO2 show a poor performance, in comparison to the reference value of this PT.