## 2 Related Works
### Recent Developments  
There are several proposals for the use of other ways of measuring radon levels, namely using active detectors, which can even be integrated into IoT systems, which in real time allows the analysis of the evolution of indoor radon concentration and its reaction, for example, to the airing of spaces, forced ventilation, seasonality, or even daily variations. For example, [PERSON] et al. (2019), within the scope of the RnMonitor project, developed a WebGIS-based platform for the expeditious in situ deployment of IoT edge devices and effective radon exposure management [60]. This project arose, according to the authors, because the available equipment was not designed for radon gas monitoring and was not present in the expedite strategy for radon assessment. Despite the potential for speeding up the process that these new methodologies present, it is still necessary to optimize the time and costs related to carrying out large-scale surveys, for example, on a national scale. Therefore, the use of existing data, such as the radiometric surveys carried out by the uranium mining industry all over the world, can allow the creation of easily accessible and inexpensive tools that can be used for the preparation of radon potential maps, ensuring that the relationship between the collected data is properly respected. There are several approaches to the elaboration of radon maps, which can be used depending on the intended purpose of the map [61]. Of the various works available, there are several that point to the use of methodologies that extend towards predicting the potential for radon emanation, such as the work presented by [PERSON] et al. (2002) [62]. These authors proposed a methodology based on the quantification of the radon emanation rate, starting from a precise characterization of the main geological site and pedological parameters that control the radon source and its transport to the soil/atmosphere interface. This methodology combines the cross-mapping analysis of these parameters into a geographic information system with a model of the vertical radon transport by diffusion in the soil. On the other hand, the elaboration of a detailed geogenic radon potential mapping based on field soil gas radon and soil gas permeability measurements, as presented by [PERSON] et al. (2014), but also by many other authors, seems to be the dominant methodology, and these maps are often the basis for the elaboration of radon maps [63]. However, if on the one hand, these maps provide reliable information for the locations where the control measurements were taken allowing the prediction with a high degree of reliability for the locations of high concentration, the same will no longer be entirely true for the locations where there is great variability in concentrations, or the soil concentration values are lower. However, even these lower values can lead to high indoor radon concentrations. [PERSON] et al. (2014) presented a modeling methodology for the analysis of radon potential based on environmental geology and geographically weighted regression and concluded that, although the results are encouraging, there are several critical issues to be addressed [64], from which it can be inferred that these maps do not dispense the confirmation of information by traditional assessment methods. As mentioned before, there are several methodologies used in the elaboration of radon maps, which are used for the most diverse purposes. As it has also been seen, the reliability of the information taken from these maps is greater the higher the number of measurements behind the map, and the more elaborate the analysis of the correlation between the various parameters that contribute to the occurrence of distinct radon emanation rates. As a first approach, it is possible to have an initial outline of the problem by drawing up a radon potential map, therefore enabling an expeditious analysis to gauge the real need of carrying out a rigorous assessment afterwards.