In the North region of Portugal, the granitic construction predominates in local buildings. Granitic buildings in this area are known to be directly related in terms of radon gas indoor air concentration, the second largest risk factor associated with lung cancer, right after tobacco. In , Curado & Lopes measured in the region of Viana do Castelo, between March and April 2016, the indoor radon gas concentration for a set of buildings with granite construction, and the results revealed concentrations that far exceed the legal limits indicated by Portuguese regulation, reaching in some cases four times higher values than the maximum reference value indicated by the WHO. Given the evidence found in , ,  and , it is imperative to develop some technologies that allow, at the same time, continuous and online monitoring of the radon concentration. Online measurements will allow the implementation of active mitigation strategies, and therefore reduce the radon gas concentration inside public buildings and consequently improve its energy efficiency.
 Curado, A., Lopes, S.I., Impact of Human Occupation on Indoor Radon Concentration: a Study Based on In-Situ Measurements for a Set of Households in Alto-Minho, Portugal. Behave 2016 – 4th European Conference on Behaviour and Energy Efficiency. Coimbra, Portugal, 8-9 September 2016.
 Veloso, B., Nogueira, J., Cardoso, M., Lung cancer and indoor radon exposure in the north of Portugal – An ecological study, 2012, Cancer Epidemiology 36, e 26-32.
 Radão: perigo que se esconde no granito, Deco Pro Teste n.º 241 – Novembro de 2003 – Páginas 37 a 39.
 Publicação: Barros-Dios, J., Ruano-Ravina, A., Pérez-Ríos, M., Castro-Bernárdez, M., Abal-Arca, J., Tojo-Castro, M., Residential radon exposure, histologic types, and lung cancer risk. A case – control study in Galicia, Spain, 2012. Cancer Epidemiology Biomarkers and Prevention 21, 951-958.