Ponta Delgada, the most densely populated city of the Azores, is located in the Picos Fissural Volcanic System on São Miguel Island. This volcanic system is located between Sete Cidades and Fogo central volcanoes and its volcanic activity has been essentially characterized by basaltic effusive eruptions. As result, this area is mainly covered by lava flows and pyroclasts of basaltic composition (s./.). Nowadays, in this volcanic system, there are no visible secondary manifestations of volcanism. Radon is a colourless and odourless radioactive gas that can be released from different types of soil and rocks, including volcanic rocks. The presence of radon is expected with bigger expression on the central volcanoes due to the presence of trachytic rocks(s./.), soil CO2 emissions and thermal anomalies; however a recent work, developed on Ponta Delgada,revealed that basaltic zones should also be taken into account in what concerns public health. As a radioactive gas, radon can represent a threat to public health when is inhaled/ingested in high concentrations for a long period of time, leading in extreme cases to lung cancer development. Indoor radon measurements in a building located in Ponta Delgada revealed indoor radon concentration above the threshold value of the regional law (150 Bq/m3). One of the compartments of the building was selected to test a set of mitigation actions. Before applying the mitigation actions, the radon concentration values measured on the selected compartment varied between 0 and 6806 Bq/m3, presenting an average value of 2056 Bq/m3. Indoor radon concentration was measured, by diffusion mode, using a Radon Scout Plus equipment. This equipment also measured air relative humidity, temperature and barometric pressure. The set of mitigation actions tested comprise natural ventilation, artificial ventilation with air extraction, artificial ventilation with air introduction and air purification. Different combinations of the different mitigation actions were tested, including different artificial ventilation velocities. Not all the tests performed were efficient; however all of them allow a reduction ofthe initial radon concentration average. Radon concentration average, during the different tests performed, varied between 6 and 1062 Bq/m3, what reveals an efficiency of remediation between 48.3 and 99.7%. Although the efficient reduction of indoor radon concentration and high efficiency percentage of some of the mitigation actions performed, a longer monitoring period should be carried out to confirm these results.