This guideline specifies requirements on bodies for periodic testing of performance tested measuring devices used for emission monitoring at small firing installations according to the Ordinance on small and medium firing installations (1st BImSchV) or the Ordinance on sweeping and checking (K?O). This includes organisational and technical requirements, the check of the equipment, the documentation of the results of the testing of the measuring devices, and the quality management system. According to paragraph 13, section 3 of 1st BImSchV, bodies for periodic testing of performance tested measuring devices are notified by the competent authority of the corresponding federal state. In the notification process meeting of different requirements on bodies testing measuring devices is checked, e.g. requirements on reliability, independence, neutrality and equipment, which are specified in this guideline.