From many years a lot of efforts have been done in order to improve in-situ radon data
monitoring and analysis, technical methodologies and mathematical modeling, with the aim
to reinforce the link between ground radon concentration anomalies and geodynamical
events. Measurements of radon gas in soil and in ground water have been carried out all
over the world and the results seem to indicate the radon as a good indicator of crustal
activity such as earthquakes. However, the current literature describing the possible
correlation between radon levels and earthquake activity uses such qualifying and caution
words as possible, apparent, limited, could, sometimes, may be, and so on.
It is clear that in some cases there are precursor changes in radon levels, but that the causal
relationship or mechanism relating these to earthquake activity is not yet well understood.
Thus, even if some results seem to suggest that geodynamical events could influence radon
concentrations, however, because of the complexity of its transport mechanism, the
correlation needs more investigations in order to clearly and firmly established it.
Further contributions can be obtained from more extended continuous data recording, in
particular near active faults, and from the comparison with other earthquake precursors.