This guideline details the requirements of DIN EN ISO/IEC 17025 on bodies performing measurements of air pollutants at stationary sources and in ambient air. The particular requirements applicable to the fields of noise and vibration are not discussed in this document. Appropriate criteria can be found, for example, in the standard DIN 45688.This guideline provides in combination with DIN EN ISO/IEC 17025 the basis for the demonstration of competence of bodies that undertake measurements of emissions from stationary sources and/or of ambient air quality, calibrations of automated measuring systems and/or performance tests. It is intended to help ensure that standardized procedures are used by bodies performing measurements of air pollutants at stationary sources and in ambient air and by laboratory accreditation bodies when implementing the criteria of DIN EN ISO/IEC 17025. The application of this guideline requires that the field of activity of the accredited body is uniquely specified. This guideline describes in the Annex fields of activities of bodies, which perform measurements in the area covered by law. This guideline is based on European Technical Specification DIN CEN/TS 15675, which species requirements on bodies for the determination of emissions from stationary sources. It includes the relevant requirements of DIN CEN/TS 15675 and amends the Technical Specification by providing clarification and additional information. Furthermore, it includes requirements on bodies for the evaluation of air pollutants in ambient air.