For many years, substandard housing has been the focus of public policies that have significantly contributed to improving the health of the French population. However, the concept of indoor air quality has only emerged recently, whereas monitoring of outdoor air pollution had already been established and well-developed for a long time. Our lifestyle leads most of us to spend more than 80%, or even 90%, of our time in enclosed spaces, whether at home or at work, in public transportation, shopping centers, or recreational facilities, etc. It is therefore impossible to ignore the potential health effects of the air we breathe in all these enclosed spaces. This is all the more true given that indoor air has its own specific characteristics compared to outdoor air: it is not simply outdoor air entering buildings through windows and ventilation systems. Construction and decoration products, furniture, cleaning supplies, DIY products, heating and hot water systems, human presence, and activities related to basic needs (cooking, hygiene, cleaning, etc.) or other activities (smoking, use of candles, incense, cosmetics, presence of pets, etc.) are all sources and vectors of the observed pollution.[chapter excerpt]