​Volcanic gases can pose a permanent threat to population, both during eruptive episodes and quiescent periods of activity. Soil diffuse degassing may be the principal hazard in inhabited areas since dangerous gases, such as CO₂, are released without being noticed by the population. This work intends to study indoor gas variations in various degassing areas of the Azores archipelago, where symptoms associated to exposure to high CO₂ concentrations were already reported. Several statistical approaches will be applied to the data in order to identify short and long-term CO₂ changes, as well as to discriminate environmental factors that may interfere with the indoor/outdoor CO₂ concentrations. Azores degassing areas will be then used as test sites to produce and validate CO₂ hazards maps, based on spatial and temporal data. Similar hazard maps are not found in the literature and constitute valuable tools for volcanic monitoring, land-use planning and public health risks assessment.