The BfS Department of Radiation Protection performs official tasks in the field of radiation protectionfor man and his environment. In this regard, the BfS functions as the co-ordinating office for allproblems concerned with the measurement of radon and its progeny, and for the task of assessingdevices for the carrying out of such measurements, as well as for the supervision of selected workactivities.In order to guarantee a high level of accuracy in all areas concerned with radon and radon progenymeasurement - these representing the major natural sources of radiation exposure - the BfS hasestablished a quality assurance management system for all measurements of this type. A set ofcalibration chambers and containers was installed in the laboratories which were subsequentlyaccredited as a German Calibration Service (DKD) Calibration Laboratory. It is licensed to act as asecondary reference laboratory for the units of radon and the potential alpha energy concentration ofits short-lived progeny, and to calibrate instruments for practical use in all fields of radon/radonprogeny measurements. The secondary standard is traced back to the national standard established atthe Federal Institute of Physics and Technology (Physikalisch-Technische Bundesanstalt, PTB), whichis at the same time the national institute for science and technology, and the highest technical authorityfor metrology in Germany. The equipment makes possible calibration for the measuring quantityconcentration of Rn-222 in air in the range between 50 Bq/m and 100 kBq/m and also for themeasuring quantity potential alpha-energy concentration (PAEC) in the range between 2 MeV/cm(3.2 E-7 J/m) and 4000 MeV/cm (6.4 E-4 J/m).