Soil air is defined as all substances in the subsurface in a gaseous state, including gases contained in artificial cavities. In the context of hazard assessments on areas suspected of being contaminated, in particular on old deposits, soil air measurements often represent a first orienting investigation if volatile organic pollutants or landfill gas are suspected.
A special form of soil air is the so-called landfill gas with its main components methane and carbon dioxide. It is produced in a landfill or old deposit by microbial decomposition of organic material. The analysis of landfill gas samples is carried out in particular if organic landfill components are suspected. In addition to a hazard assessment, the phase of landfill gas development (degradation stages of the organic material) can also be determined.
The Council of Environmental Advisers (SRU) defines "indoor spaces" as apartments with living rooms, bedrooms, handicrafts, sports and cellar rooms, kitchens and bathrooms, as well as workspaces in buildings that are not subject to the scope of the Ordinance on Hazardous Substances (GefStoffV) with regard to hazardous substances, such as offices. This also includes interiors in public buildings (hospitals, schools, day-care centres, sports halls, libraries, restaurants, theatres, cinemas and other public event rooms) as well as the interiors of motor vehicles and public transport. Indoor pollutants can pose a significant health hazard. Particularly in existing buildings from the 1970s, problematic building materials (residential poisons) can be found, which can still pose a health hazard today. Even though many hazardous substances may no longer be used, existing buildings must continue to be examined for their hazard potential or their need for renovation.