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Indoor Air Quality

Schimmelbefall in einer Küche © LGA

Air is among the basic essentials of human being. In the highly-developed industrial countries, people stay indoors more than 80% of time on average; therefore a great importance is attached to indoor air quality.
In addition to temperature, relative air humidity, and rate of air exchange, air pollutions from different sources can affect indoor air quality.

From an analytic point of view, a distinction into the following emissions is meaningful:

Chemical gases and vapours (e.g. carbon monoxide, formaldehyde, solvents, biocides)
Aerosols and particulate matter including nano-particles (e.g. soot, tobacco smoke)
Biological air pollutants (e.g. moulds, mites, bacteria and other micro-organisms)

Semi-volatile compounds, such as many pesticides, are distributed indoors not gaseously, but bound to particles; they might have derived both from primary and secondary sources. Sometimes these materials have been produced indoors intentionally (e.g. scents) or unintentionally, for example pollutions from building products or articles of interior decoration (e.g. VOC emissions). Certain cases of damages, such as dampness damage, can become a source of emission due to mould attack. The emitted compounds can be of natural origin, such as radon, or of anthropogenic origin, such as wood preservatives. The extent of their occurrence depends on the power and dimension of existing sources in relation to the room size, on the indoor activities (e.g. tobacco smoke) as well as on ventilation and cleaning behaviour of the users. Due to the present trend to low-energy buildings having a very close structural covering and potentially showing an insufficient air interchange rate, the quality of the interior air can still gain in importance in future.

The compounds can cause toxic effects (e.g. allergic, immune-toxic, irritant or infectious effects) dependent on their nature, their concentration, the duration of exposition, and the disposition of the residents. Their presence is partly noticed olfactory. Environmentally associated health effects such as Multiple Chemical Sensitivity (MCS) are referred by the residents frequently to the interior.

For a number of indoor pollutants such as formaldehyde, toxicologically based guideline values have been developed on a national or European level (e.g. WHO Air Quality Guidelines). However, limit values for indoor pollutants have been established by law only in special singular cases.