external exposure facility Radon calibration laboratory The Radon Calibration Laboratory of the German Federal Office for Radiation Protection (BfS) in Berlin provides reference radon atmospheres at concentrations from 0.5–100 kBq/m³ for the calibration and testing of radon measurement devices. It operates controlled radon chambers under well-defined conditions of radon concentration, humidity and temperature, and supports national and international instrument intercomparisons. The facility also performs research on radon measurement methodology and access is by prior appointment. Located at BfS. Paul Schofield website