There are a number of potential sources of volatile organic compounds in indoor spaces. They can be divided into the following three categories:
Almost any of the materials used in modern buildings can constitute a building-related VOC source. The range of substances reflects the changes in the composition of the materials used. For instance, more dibasic esters (DBEs) - a substance category that is used as a substitute for conventional solvents - will be detected in the future. In addition, materials such as bricks, mortar and other elements of buildings, which used to be low in emissions, now contain aggregates that have plastics and solvents in them. Other potential sources are wall panelling, floor coverings, insulation materials, sealants, furniture, paints, varnishes and solvents used in interiors.
Human activities cause VOCs to enter rooms in the form of cleaning and furniture care products, cosmetics, disinfectants, plant protection products and, sometimes, tobacco. VOC contamination is also possible through the outdoor air (e.g. from road traffic).
When identifying potential VOC sources, the first step should be to ascertain whether redecoration work has been carried out or new furniture, equipment, etc. installed recently. In such cases, the VOC concentrations can often be reduced by ventilating the room for a prolonged period.
A key parameter in any assessment of indoor air quality is the total of the VOCs in the 50 to 260°C boiling range, referred to as TVOCs (total volatile organic compounds). Although there are no substantiated dose-effect relationships and TVOC concentrations should not be used as the sole criterion when assessing the healthiness of indoor air quality, the TVOC concentration levels can be used to assess VOC-related adverse effects on the indoor air. For instance, the probability of irritation and perception of odours increases as the TVOC concentration rises. The German Committee on Indoor Guide Values recommends Seifert’s five-level approach from 1999 for assessing TVOC concentration levels.