Furnas Volcano is one of the most important active volcanoes of S. Miguel Island and displays the most significant degassing areas of the Azores archipelago, including fumarolic fields, cold and thermal springs and soil diffuse degassing. Since the early nineties some CO₂ soil concentration surveys have been carried out at Furnas Volcano caldera. The obtained results showed that one of the major degassing areas extends below Furnas village, explaining the death of animals and the dizziness of people reported to have occurred in the area.

In order to analyse the CO₂ flux behaviour and to identify seismovolcanic precursors a continuous CO₂ flux station with coupled environmental sensors was installed at Furnas village degassing area, in October 2001. To discriminate the presence of volcanic signals from external interferences, statistical methods were applied to the recorded data series, namely multiple regression analysis. The results showed that the monitored environmental parameters account for 30,5% of the flux variation, indicating that some meteorological conditions such as low barometric pressure and high rainfall events are responsible for significant increases in CO₂ flux.

To study these implications in the inhabited area a monitoring test was conducted in a dwelling located where CO₂ soil concentration is higher than 50%. In this setting, the indoor CO₂ air concentration at the floor level reached values as higher as 20,8% during stormy weather periods showing that high risk conditions can occur exclusively by the influence of environmental factors. Such conclusion indicates that even though Furnas Volcano is currently at rest, the population is at permanent risk from exposure to CO₂.