Calibration by dynamic dilution gas analysers for monitoring air pollution and air emissions_vrevised

− The monitoring of air pollution and air emissions has suffered a great evolution during last decade in Portugal. In relation with this evolution, the necessary metrological control for the measurement equipments increased substantially, as required from the European Norm EN ISO/IEC 17025 [1]. This work compares two alternative methodologies to calibrate equipments for monitoring air pollutants emitted from ducts and stacks to the atmosphere. The traditional method, by comparing the calibration gases, Certified Reference Materials (CRM) with the equipment measurements and other method that consists in generate the calibration gas by dynamic dilution method from a high concentration CRM for each quantity. The dilution systems that use Mass Flow Controllers (MFC) are very suitable on this field. They also give some technical advantages in calibration process, but a bigger expanded uncertainty is reached, influenced first by the MFC. When comparing dynamic dilution and traditional calibration methods for some measurement reference equipments by Z’ – score and En methods, the results were satisfactory.