Title: BfS-report-2019 (1).pdf
The calibration object is placed into a calibration container, which is made of stainless steel and which contains a radon-222 reference atmosphere (volume see “Operating conditions”). The radon-222 activity concentration in the container is kept approximately constant before and during the period of calibration. The reference value of the radon-222 activity concentration in the calibration container (Cres) is measured by scintillation cells as working standards. Their measurand is traceable to national standards at the Physikalisch-Technische Bun- desanstalt (PTB). After reaching the equilibrium state of the calibration object’s indication values the calibration period begins, which has a defined duration (tw). From all single indication values for the radon-222 activity concentration of the calibration object the arithmetic mean Cw is determined for the calibration period. The corresponding reference value Cresis determined from sampling with the working standard, whereas the instru-