Radon (222Rn) gas is the largest source of public exposure to naturally occurring radioactivity and the identification of radon priority areas is required by the Council Directive 2013/59/Euratom. Radon is also used as a tracer to improve atmospheric transport models and to indirectly estimate greenhouse gas (GHG) fluxes using the Radon Tracer Method (RTM). This method is based on the correlation between atmospheric concentrations of radon and GHG, together with information on the radon flux data. For radiological data, all European countries have installed networks of automatic gamma dose rate monitoring stations and report the real-time information gathered to the European Radiological Data Exchange Platform (EURDEP). So far, atmospheric radon activity concentrations and radon fluxes are not yet reported in EURDEP, nor routinely measured within the European radiological networks although these observations could help to avoid false positives results. Due to above applications, there is a need of building a metrological chain to ensure high quality radon activity concentrations and radon flux measurements. Both climate and radiation protection research communities underline the need for improved traceability in low-level atmospheric radon measurements (Khanbabaee et al., 2021). The EMPIR project 19ENV01 traceRadon1 is aimed towards providing the necessary measurement infrastructure and transfer standards to fulfil this need. Results of this project are particularly important for improving independent GHG emission estimates that support national reporting under the Paris Agreement on climate change and for the Council Directive 2013/59/Euratom, thus benefitting two large scientific communities. In this paper, early results, such as new activity standard developments and an overview of commercial and research radon monitors are presented and discussed. These results will feed into the traceRadon project with respect to radionuclide metrology in air and its potential for the improvement of the RTM.
