Radon survey in active volcanoes

World active volcanoes are about 500. Volcanic eruptions are one of the most impressive, destructive, and terrifying of natural phenomena. For this reason Volcano survey is one of the most important scientific topics. The attention is posed on its potential destructive power. Several researchers have studied, in particular, possible volcanic eruption precursors. The mayor studies have historically interested volcanic tremor and soil deformations. Studies have also been performed on fumaroles on CO2 gas flux. In the last years a new kind of investigation has been carried out. Many researchers have been performed on in soil radon gas survey in volcanic area. Different methodologies are applied for measuring radon gas. Most of them use in-soil continuous measurements other one passive technique. This last are most used to characterize the area. Available data are reported from in-soil radon measurements, carried out in different volcanoes all over the world with particular attention to the results obtained on Mt. Etna, the biggest European active volcano. Even if the results strongly suggest that volcanic activity, in particular magma uprising, could influence Radon values detected over or near a volcanic edifice, however, because of the very complexity of such systems, the correlation needs more investigations in order to clearly and firmly established it.