People spend an average of 90% of their time in indoor environments.
There is a long list of indoor sources that can contribute to increased
pollutant concentrations, some of them related to human activities
(e.g. people’s movement, cooking, cleaning, smoking), but also to
surface chemistry reactions with human skin and building and furniture
surfaces. The result of all these emissions is a heterogeneous
cocktail of pollutants with varying degrees of toxicity, which makes
indoor air quality a complex system. Good characterization of the
sources that affect indoor air pollution levels is of major importance for
quantifying (and reducing) the associated health risks. This chapter
reviews some of the more significant indoor sources that can be found
in the most common non-occupational indoor environments.